1.1 Field of the Invention
The present invention relates generally to the fields of molecular biology. More particularly, certain embodiments concern methods and compositions comprising DNA segments, and proteins derived from bacterial species. More particularly, it concerns novel genes from Bacillus thuringiensis encoding lepidopteran-toxic crystal proteins. Various methods for making and using these DNA segments, DNA segments encoding synthetically-modified Cry proteins, and native and synthetic crystal proteins are disclosed, such as, for example, the use of DNA segments as diagnostic probes and templates for protein production, and the use of proteins, fusion protein carriers and peptides in various immunological and diagnostic applications. Also disclosed are methods of making and using nucleic acid segments in the development of transgenic plant cells containing the DNA segments disclosed herein.
1.2 Description of the Related Art
Almost all field crops, plants, and commercial farming areas are susceptible to attack by one or more insect pests. Particularly problematic are Coleopteran and Lepidoptern pests. For example, vegetable and cole crops such as artichokes, kohlrabi, arugula, leeks, asparagus, lentils, beans, lettuce (e.g., head, leaf, romaine), beets, bok choy, malanga, broccoli, melons (e.g., muskmelon, watermelon, crenshaw, honeydew, cantaloupe), brussels sprouts, cabbage, cardoni, carrots, napa, cauliflower, okra, onions, celery, parsley, chick peas, parsnips, chicory, peas, chinese cabbage, peppers, collards, potatoes, cucumber, pumpkins, cucurbits, radishes, dry bulb onions, rutabaga, eggplant, salsify, escarole, shallots, endive, soybean, garlic, spinach, green onions, squash, greens, sugar beets, sweet potatoes, turnip, swiss chard, horseradish, tomatoes, kale, turnips, and a variety of spices are sensitive to infestation by one or more of the following insect pests: alfalfa looper, armyworm, beet armyworm, artichoke plume moth, cabbage budworm, cabbage looper, cabbage webworm, corn earworm, celery leafeater, cross-striped cabbageworm, european corn borer, diamondback moth, green cloverworm, imported cabbageworm, melonworm, omnivorous leafroller, pickleworm, rindworm complex, saltmarsh caterpillar, soybean looper, tobacco budworm, tomato fruitworm, tomato hornworm, tomato pinworm, velvetbean caterpillar, and yellowstriped armyworm. Likewise, pasture and hay crops such as alfalfa, pasture grasses and silage are often attacked by such pests as armyworm, beef armyworm, alfalfa caterpillar, European skipper, a variety of loopers and webworms, as well as yellowstriped armyworms.
Fruit and vine crops such as apples, apricots, cherries, nectarines, peaches, pears, plums, prunes, quince almonds, chestnuts, filberts, pecans, pistachios, walnuts, citrus, blackberries, blueberries, boysenberries, cranberries, currants, loganberries, raspberries, strawberries, grapes, avocados, bananas, kiwi, persimmons, pomegranate, pineapple, tropical fruits are often susceptible to attack and defoliation by achema sphinx moth, amorbia, armyworm, citrus cutworm, banana skipper, blackheaded fireworm, blueberry leafroller, cankerworm, cherry fruitworm, citrus cutworm, cranberry girdler, eastern tent caterpillar, fall webworm, fall webworm, filbert leafroller, filbert webworm, fruit tree leafroller, grape berry moth, grape leaffolder, grapeleaf skeletonizer, green fruitworm, gummosos-batrachedra commosae, gypsy moth, hickory shuckworm, hornworms, loopers, navel orangeworm, obliquebanded leafroller, omnivorous leafroller. omnivorous looper, orange tortrix, orangedog, oriental fruit moth, pandemis leafroller, peach twig borer, pecan nut casebearer, redbanded leafroller, redhumped caterpillar, roughskinned cutworm, saltmarsh caterpillar, spanworm, tent caterpillar, thecla-thecla basillides, tobacco budworm, tortrix moth, tufted apple budmoth, variegated leafroller, walnut caterpillar, western tent caterpillar, and yellowstriped armyworm.
Field crops such as canola/rape seed, evening primrose, meadow foam, corn (field, sweet, popcorn), cotton, hops, jojoba, peanuts, rice, safflower, small grains (barley, oats, rye, wheat, etc.), sorghum, soybeans, sunflowers, and tobacco are often targets for infestation by insects including armyworm, asian and other corn borers, banded sunflower moth, beet armyworm, bollworm, cabbage looper, corn rootworm (including southern and western varieties), cotton leaf perforator, diamondback moth, european corn borer, green cloverworm, headmoth, headworm, imported cabbageworm, loopers (including Anacamptodes spp.), obliquebanded leafroller, omnivorous leaftier, podworm, podworm, saltmarsh caterpillar, southwestern corn borer, soybean looper, spotted cutworm, sunflower moth, tobacco budworm, tobacco hornworm, velvetbean caterpillar.
Bedding plants, flowers, ornamentals, vegetables and container stock are frequently fed upon by a host of insect pests such as armyworm, azalea moth, beet armyworm, diamondback moth, ello moth (hornworm), Florida fern caterpillar, Io moth, loopers, oleander moth, omnivorous leafroller, omnivorous looper, and tobacco budworm.
Forests, fruit, ornamental, and nut-bearing trees, as well as shrubs and other nursery stock are often susceptible to attack from diverse insects such as bagworm, blackheaded budworm, browntail moth, california oakworm, douglas fir tussock moth, elm spanworm, fall webworm, fruittree leafroller, greenstriped mapleworm, gypsy moth, jack pine budworm, mimosa webworm, pine butterfly, redhumped caterpillar, saddleback caterpillar, saddle prominent caterpillar, spring and fall cankerworm, spruce budworm, tent caterpillar, tortrix, and western tussock moth. Likewise, turf grasses are often attacked by pests such as armyworm, sod webworm, and tropical sod webworm.
Because crops of commercial interest are often the target of insect attack, environmentally-sensitive methods for controlling or eradicating insect infestation are desirable in many instances. This is particularly true for farmers, nurserymen, growers, and commercial and residential areas which seek to control insect populations using eco-friendly compositions.
The most widely used environmentally-sensitive insecticidal formulations developed in recent years have been composed of microbial pesticides derived from the bacterium Bacillus thuringiensis. B. thuringiensis is a Gram-positive bacterium that produces crystal proteins or inclusion bodies which are specifically toxic to certain orders and species of insects. Many different strains of B. thuringiensis have been shown to produce insecticidal crystal proteins. Compositions including B. thuringiensis strains which produce insecticidal proteins have been commercially-available and used as environmentally-acceptable insecticides because they are quite toxic to the specific target insect, but are harmless to plants and other non-targeted organisms.
1.2.1 B. thuiungiensis Crystal Proteins
1.2.1 xcex4-Endotoxins
xcex4-endotoxins are used to control a wide range of leaf-eating caterpillars and beetles, as well as mosquitoes. These proteinaceous parasporal crystals, also referred to as insecticidal crystal proteins, crystal proteins, Bt inclusions, crystaline inclusions, inclusion bodies, and Bt toxins, are a large collection of insecticidal proteins produced by B. thuringiensis that are toxic upon ingestion by a susceptible insect host. Over the past decade research on the structure and function of B. thuringiensis toxins has covered all of the major toxin categories, and while these toxins differ in specific structure and function, general similarities in the structure and function are assumed. Based on the accumulated knowledge of B. thuringiensis toxins, a generalized mode of action for B. thuringiensis toxins has been created and includes: ingestion by the insect, solubilization in the insect midgut (a combination stomach and small intestine), resistance to digestive enzymes sometimes with partial digestion actually xe2x80x9cactivatingxe2x80x9d the toxin, binding to the midgut cells, formation of a pore in the insect cells and the disruption of cellular homeostasis (English and Slatin, 1992).
One of the unique features of B. thuringiensis is its production of crystal proteins during sporulation which are specifically toxic to certain orders and species of insects. Many different strains of B. thuringiensis have been shown to produce insecticidal crystal proteins. Compositions including B. thuringiensis strains which produce proteins having insecticidal activity against lepidopteran and dipteran insects have been commercially available and used as environmentally-acceptable insecticides because they are quite toxic to the specific target insect, but are harmless to plants and other non-targeted organisms.
The mechanism of insecticidal activity of the B. thuringiensis crystal proteins has been studied extensively in the past decade. It has been shown that the crystal proteins are toxic to the insect only after ingestion of the protein by the insect. The alkaline pH and proteolytic enzymes in the insect mid-gut solubilize the proteins, thereby allowing the release of components which are toxic to the insect. These toxic components disrupt the mid-gut cells, cause the insect to cease feeding, and, eventually, bring about insect death. For this reason, B. thuringiensis has proven to be an effective and environmentally safe insecticide in dealing with various insect pests.
As noted by Hxc3x6fte and Whiteley (1989), the majority of insecticidal B. thuringiensis strains are active against insects of the order Lepidoptera, i.e., caterpillar insects. Other B. thuringiensis strains are insecticidally active against insects of the order Diptera, i.e., flies and mosquitoes, or against both lepidopteran and dipteran insects. In recent years, a few B. thuringiensis strains have been reported as producing crystal proteins that are toxic to insects of the order Coleoptera, i.e., beetles (Krieg et al., 1983; Sick et al., 1990; Donovan et al., 1992; Lambert et al., 1992a; 1992b).
1.2.2 Genes Encoding Crystal Proteins
Many of the xcex4-endotoxins are related to various degrees by similarities in their amino acid sequences. Historically, the proteins and the genes which encode them were classified based largely upon their spectrum of insecticidal activity. The review by Hxc3x6fie and Whiteley (1989) discusses the genes and proteins that were identified in B. thuringiensis prior to 1990, and sets forth the nomenclature and classification scheme which has traditionally been applied to B. thuringiensis genes and proteins. cryI genes encode lepidopteran-toxic CryI proteins. cryII genes encode CryII proteins that are toxic to both lepidopterans and dipterans. cryIII genes encode coleopteran-toxic CryIII proteins, while cryIV genes encode dipteran-toxic CryIV proteins. Based on the degree of sequence similarity, the proteins were further classified into subfamilies; more highly related proteins within each family were assigned divisional letters such as CryIA, CryIB, CryIC, etc. Even more closely related proteins within each division were given names such as CryIC1, CryIC2, etc.
Recently, a new nomenclature was developed which systematically classified the Cry proteins based upon amino acid sequence homology rather than upon insect target specificities (Crickmore et al., 1998). The classification scheme for many known toxins, including allelic variations in individual proteins, the relevant information can be found on websites. The informationw was most recently updated as of Apr. 27, 1999 and is herein incorporated by reference.
1.2.3 Crystal Proteins Toxic to Lepidopteran Insects
The recent review by Schnepf et al. (1998) describes the enormous diversity of insecticidal crystal proteins derived from B. thuringiensis. Cry proteins of the Cry1, Cry2, and Cry9 classes are particularly known for their toxicity towards lepidopteran larvae, however, the degree of toxicity varies significantly depending on the target lepidopteran pest (Hxc3x6fte and Whiteley, 1989). For instance, Cry1Ac shows poor toxicity towards the armyworm, Spodoptera littoralis, but strong toxicity towards the tobacco budworm, Heliothis virescens. In addition, slight variations in amino acid sequence within a Cry protein class can dramatically impact insecticidal activity (see Schnepf et al., 1998 and references therein). The Cry3Ba and Cry3Bb genes, for instance, share 94% amino acid sequence identity, but only Cry3Bb exhibits significant toxicity towards the Southern corn rootwom, Diabrotica undecimpunctata howardi (Donovan et al., 1992). Similarly, Cry2Aa and Cry2Ab share 87% amino acid sequence identity, yet only Cry2Aa displays toxicity towards mosquitos (Widner and Whiteley, 1990). Von Tersch et al. (1991) demonstrated that Cry1Ac proteins varying by only seven amino acids ( greater than 99% sequence identity) nevertheless show significant differences in insecticidal activity. Lee et al. (1996) reported that Cry1Ab alleles differing at only two amino acid positions exhibited a 10-fold difference in toxicity towards the gypsy moth, Lymantria dispar. Thus, even Cry proteins that are considered to be alleles of known Cry proteins or to belong to a Cry protein subclass (Crickmore et al., 1998) may have unique and useful insecticidal properties. International Patent Application Publication No. WO 98/00546 and WO 98/40490 describe a variety of Cry1-, Cry2-, and Cry9-related crystal proteins obtained from B. thuringiensis. 
2.1 Cry DNA Segments
The present invention concerns nucleic acid segments, that can be isolated from virtually any source, that are free from total genomic DNA and that encode the novel peptides disclosed herein. Nucleic acid segments encoding these polypeptides may encode active proteins, peptides or peptide fragments, polypeptide subunits, functional domains, or the like of one or more crystal proteins. In addition the invention encompasses nucleic acid segments which may be synthesized entirely in vitro using methods that are well-known to those of skill in the art which encode the novel Cry polypeptides, peptides, peptide fragments, subunits, or functional domains disclosed herein.
As used herein, the term xe2x80x9cnucleic acid segmentxe2x80x9d refers to a polynucleotide molecule that has been isolated free of total genomic DNA of a particular species. Therefore, a nucleic acid segment encoding an endotoxin polypeptide refers to a nucleic acid segment that comprises one or more crystal protein-encoding sequences yet is isolated away from, or purified free from, total genomic DNA of the species from which the nucleic acid segment is obtained, which in the instant case is the genome of the Gram-positive bacterial genus, Bacillus, and in particular, the species of Bacillus known as B. thuringiensis. Included within the term xe2x80x9cnucleic acid segmentxe2x80x9d, are polynucleotide segments and smaller fragments of such segments, and also recombinant vectors, including, for example, plasmids, cosmids, phagemids, phages, viruses, and the like.
Similarly, a DNA segment comprising an isolated or purified crystal protein-encoding gene refers to a DNA segment which may include in addition to peptide encoding sequences, certain other elements such as, regulatory sequences, isolated substantially away from other naturally occurring genes or protein-encoding sequences. In this respect, the term xe2x80x9cgenexe2x80x9d is used for simplicity to refer to a functional protein-, polypeptide- or peptide-encoding unit. As will be understood by those in the art, this functional term includes both genomic sequences, operon sequences and smaller engineered gene segments that express, or may be adapted to express, proteins, polypeptides or peptides. Also, the term includes an expression cassette comprising at least a promoter operably linked to one or more protein coding sequences, operably linked to at least a transcriptional termination sequence.
xe2x80x9cIsolated substantially away from other coding sequencesxe2x80x9d means that the gene of interest, in this case, a nucleic acid segment or gene encoding all or part of a bacterial insecticidal crystal protein, forms the significant part of the coding region of the DNA segment, and that the DNA segment does not contain large portions of naturally-occurring coding DNA, such as large chromosomal fragments or other functional nucleic acid segments or genes or operon coding regions. Of course, this refers to the DNA segment as originally isolated, and does not exclude genes, recombinant genes, synthetic linkers, or coding regions later added to the segment by the hand of man.
In particular embodiments, the invention concerns isolated DNA segments and recombinant vectors incorporating DNA sequences that encode a Cry peptide species that includes within its amino acid sequence an amino acid sequence essentially as set forth in SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:50 and SEQ ID NO. 63.
The term xe2x80x9ca sequence essentially as set forth in SEQ ID NO:2, SEQ ID NO:4, or SEQ ID NO:6,xe2x80x9d for example, means that the sequence substantially corresponds to a portion of the sequence of SEQ ID NO:2, SEQ ID NO:4, or SEQ ID NO:6 and has relatively few amino acids that are not identitical with, or a biologically functional equivalent of, the amino acids of any of these sequences. The term xe2x80x9cbiologically functional equivalentxe2x80x9d is well understood in the art and is further defined in detail herein (e.g., see Illustrative Embodiments). Accordingly, sequences that have from about 70% to about 80%, or more preferably about 81, 82, 83, 84, 85, 86, 87, 88, 89, or about 90%, or even more preferably about 91, 92, 93, 94, 95, 96, 97, 98, or about 99% amino acid sequence identity or functional equivalence to the amino acids of SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:50 and SEQ ID NO. 63 will be sequences that are xe2x80x9cessentially as set forth in SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:50 and SEQ ID NO: 63.xe2x80x9d
In addition, sequences that have from about 70% to about 80%, or more preferably about 81, 82, 83, 84, 85, 86, 87, 88, 89, or about 90%, or even more preferably about 91, 92, 93, 94, 95, 96, 97, 98, or about 99% nucleic acid sequence identity or functional equivalence to the nucleic acids of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62 will be sequences that are xe2x80x9cessentially as set forth in SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62.xe2x80x9d
It will also be understood that amino acid and nucleic acid sequences may include additional residues, such as additional N- or C-terminal amino acids or 5xe2x80x2 or 3xe2x80x2 sequences, and yet still be essentially as set forth in one of the sequences disclosed herein, so long as the sequence meets the criteria set forth above, including the maintenance of biological protein activity where protein expression is concerned. The addition of terminal sequences particularly applies to nucleic acid sequences that may, for example, include various non-coding sequences flanking either of the 5xe2x80x2 or 3xe2x80x2 portions of the coding region or may include various internal sequences, i.e., introns, which are known to occur within genes.
The nucleic acid segments of the present invention, regardless of the length of the coding sequence itself, may be combined with other DNA sequences, such as promoters, polyadenylation signals, additional restriction enzyme sites, multiple cloning sites, other coding segments, and the like, such that their overall length may vary considerably. It is therefore contemplated that a nucleic acid fragment of almost any length may be employed, with the total length preferably being limited by the ease of preparation and use in the intended recombinant DNA protocol. For example, nucleic acid fragments may be prepared that include a short contiguous stretch encoding any of the peptide sequences disclosed in SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:50 and SEQ ID NO: 63, or that are identical with or complementary to DNA sequences which encode any of the peptides disclosed in SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:50 and SEQ ID NO: 63, and particularly those DNA segments disclosed in SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62. For example, DNA sequences such as about 18 nucleotides, and that are up to about 10,000, about 5,000, about 3,000, about 2,000, about 1,000, about 500, about 200, about 100, about 50, and about 14 base pairs in length (including all intermediate lengths) are also contemplated to be useful.
It will be readily understood that xe2x80x9cintermediate lengthsxe2x80x9d, in these contexts, means any length between the quoted ranges, such as 18, 19, 20, 21, 22, 23, etc.; 30, 31, 32, etc.; 50, 51, 52, 53, etc.; 100, 101, 102, 103, etc.; 150, 151, 152, 153, etc.; including all integers in the ranges of from about 200-500; 500-1,000; 1,000-2,000; 2,000-3,000; 3,000-5,000; and up to and including sequences of about 10,00 or so nucleotides and the like.
It will also be understood that this invention is not limited to the particular nucleic acid sequences which encode peptides of the present invention, or which encode the amino acid sequences of SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:50 and SEQ ID NO: 63, including those DNA sequences which are particularly disclosed in SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62. Recombinant vectors and isolated DNA segments may therefore variously include the peptide-coding regions themselves, coding regions bearing selected alterations or modifications in the basic coding region, or they may encode larger polypeptides that nevertheless include these peptide-coding regions or may encode biologically functional equivalent proteins or peptides that have variant amino acids sequences.
The DNA segments of the present invention encompass biologically-functional, equivalent peptides. Such sequences may arise as a consequence of codon degeneracy and functional equivalency that are known to occur naturally within nucleic acid sequences and the proteins thus encoded. Alternatively, functionally-equivalent proteins or peptides may be created via the application of recombinant DNA technology, in which changes in the protein structure may be engineered, based on considerations of the properties of the amino acids being exchanged. Changes designed by man may be introduced through the application of site-directed mutagenesis techniques, e.g., to introduce improvements to the antigenicity of the protein or to test mutants in order to examine activity at the molecular level.
If desired, one may also prepare fusion proteins and peptides, e.g., where the peptide-coding regions are aligned within the same expression unit with other proteins or peptides having desired functions, such as for purification or immunodetection purposes (e.g., proteins that may be purified by affinity chromatography and enzyme label coding regions, respectively).
Recombinant vectors form further aspects of the present invention. Particularly useful vectors are contemplated to be those vectors in which the coding portion of the DNA segment, whether encoding a full length protein or smaller peptide, is positioned under the control of a promoter. The promoter may be in the form of the promoter that is naturally associated with a gene encoding peptides of the present invention, as may be obtained by isolating the 5xe2x80x2 non-coding sequences located upstream of the coding segment or exon, for example, using recombinant cloning and/or PCR(trademark) technology, in connection with the compositions disclosed herein.
2.2 Cry DNA Segments as Hybridization Probes and Primers
In addition to their use in directing the expression of crystal proteins or peptides of the present invention, the nucleic acid sequences contemplated herein also have a variety of other uses. For example, they also have utility as probes or primers in nucleic acid hybridization embodiments. As such, it is contemplated that nucleic acid segments that comprise a sequence region that consists of at least a 14 nucleotide long contiguous sequence that has the same sequence as, or is complementary to, a 14 nucleotide long contiguous DNA segment of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62 will find particular utility. Longer contiguous identical or complementary sequences, e.g., those of about 20, 30, 40, 50, 100, 200, 500, 1000, 2000, 5000 bp, etc. (including all intermediate lengths and up to and including the full-length gene sequences encoding each polypeptide will also be of use in certain embodiments.
The ability of such nucleic acid probes to specifically hybridize to crystal protein-encoding sequences will enable them to be of use in detecting the presence of complementary sequences in a given sample. However, other uses are envisioned, including the use of the sequence information for the preparation of mutant species primers, or primers for use in preparing other genetic constructions.
Nucleic acid molecules having sequence regions consisting of contiguous nucleotide stretches of about 14 to about 17 or so, 18-25, 26-35, 36-50, or even up to and including sequences of about 100-200 nucleotides or so, identical or complementary to DNA sequences of SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62, are particularly contemplated as hybridization probes for use in, e.g., Southern and Northern blotting. Smaller fragments will generally find use in hybridization embodiments, wherein the length of the contiguous complementary region may be varied, such as between about 10-14 and about 100 to 200 or so nucleotides, but larger contiguous complementarity stretches may be used, according to the length complementary sequences one wishes to detect.
Of course, fragments may also be obtained by other techniques such as, e.g., by mechanical shearing or by restriction enzyme digestion. Small nucleic acid segments or fragments may be readily prepared by, for example, directly synthesizing the fragment by chemical means, as is commonly practiced using an automated oligonucleotide synthesizer. Also, fragments may be obtained by application of nucleic acid reproduction technology, such as the PCR(trademark) technology of U.S. Pat. Nos. 4,683,195 and 4,683,202 (each incorporated herein by reference), by introducing selected sequences into recombinant vectors for recombinant production, and by other recombinant DNA techniques generally known to those of skill in the art of molecular biology.
Accordingly, the nucleotide sequences of the invention may be used for their ability to selectively form duplex molecules with complementary stretches of DNA fragments. Depending on the application envisioned, one will desire to employ varying conditions of hybridization to achieve varying degrees of selectivity of probe towards target sequence. For applications requiring high selectivity, one will typically desire to employ relatively stringent conditions to form the hybrids, e.g., one will select relatively low salt and/or high temperature conditions, such as provided by about 0.02 M to about 0.15 M NaCl at temperatures of about 50xc2x0 C. to about 70xc2x0 C. Such selective conditions tolerate little, if any, mismatch between the probe and the template or target strand, and would be particularly suitable for isolating crystal protein-encoding DNA segments. Detection of DNA segments via hybridization is well-known to those of skill in the art, and the teachings of U.S. Pat. Nos. 4,965,188 and 5,176,995 (each incorporated herein by reference) are exemplary of the methods of hybridization analyses. Teachings such as those found in the texts of Maloy et al., 1990; Maloy 1994; Segal, 1976; Prokop, 1991; and Kuby, 1991, are particularly relevant.
Of course, for some applications, for example, where one desires to prepare mutants employing a mutant primer strand hybridized to an underlying template or where one seeks to isolate crystal protein-encoding sequences from related species, functional equivalents, or the like, less stringent hybridization conditions will typically be needed in order to allow formation of the heteroduplex. In these circumstances, one may desire to employ conditions such as about 0.15 M to about 0.9 M salt, at temperatures ranging from about 20xc2x0 C. to about 55xc2x0 C. Cross-hybridizing species can thereby be readily identified as positively hybridizing signals with respect to control hybridizations. In any case, it is generally appreciated that conditions can be rendered more stringent by the addition of increasing amounts of formamide, which serves to destabilize the hybrid duplex in the same manner as increased temperature. Thus, hybridization conditions can be readily manipulated, and thus will generally be a method of choice depending on the desired results.
In certain embodiments, it will be advantageous to employ nucleic acid sequences of the present invention in combination with an appropriate means, such as a label, for determining hybridization. A wide variety of appropriate indicator means are known in the art, including fluorescent, radioactive, enzymatic or other ligands, such as avidin/biotin, which are capable of giving a detectable signal. In preferred embodiments, one will likely desire to employ a fluorescent label or an enzyme tag, such as urease, alkaline phosphatase or peroxidase, instead of radioactive or other environmentally undesirable reagents. In the case of enzyme tags, colorimetric indicator substrates are known that can be employed to provide a means visible to the human eye or spectrophotometrically, to identify specific hybridization with complementary nucleic acid-containing samples.
In general, it is envisioned that the hybridization probes described herein will be useful both as reagents in solution hybridization as well as in embodiments employing a solid phase. In embodiments involving a solid phase, the test DNA (or RNA) is adsorbed or otherwise affixed to a selected matrix or surface. This fixed, single-stranded nucleic acid is then subjected to specific hybridization with selected probes under desired conditions. The selected conditions will depend on the particular circumstances based on the particular criteria required (depending, for example, on the G+C content, type of target nucleic acid, source of nucleic acid, size of hybridization probe, etc.). Following washing of the hybridized surface so as to remove nonspecifically bound probe molecules, specific hybridization is detected, or even quantitated, by means of the label.
2.3 Vectors and Methods for Recombinant Expression of Cry Polypeptides
In other embodiments, it is contemplated that certain advantages will be gained by positioning the coding DNA segment under the control of a recombinant, or heterologous, promoter. As used herein, a recombinant or heterologous promoter is intended to refer to a promoter that is not normally associated with a DNA segment encoding a crystal protein or peptide in its natural environment. Such promoters may include promoters normally associated with other genes, and/or promoters isolated from any bacterial, viral, eukaryotic, or plant cell. Naturally, it will be important to employ a promoter that effectively directs the expression of the DNA segment in the cell type, organism, or even animal, chosen for expression. The use of promoter and cell type combinations for protein expression is generally known to those of skill in the art of molecular biology, for example, see Sambrook et al., 1989. The promoters employed may be constitutive, or inducible, and can be used under the appropriate conditions to direct high level expression of the introduced DNA segment, such as is advantageous in the large-scale production of recombinant proteins or peptides. Appropriate promoter systems contemplated for use in high-level expression include, but are not limited to, the Pichia expression vector system (Pharmacia LKB Biotechnology).
In connection with expression embodiments to prepare recombinant proteins and peptides, it is contemplated that longer DNA segments will most often be used, with DNA segments encoding the entire peptide sequence being most preferred. However, it will be appreciated that the use of shorter DNA segments to direct the expression of crystal peptides or epitopic core regions, such as may be used to generate anti-crystal protein antibodies, also falls within the scope of the invention. DNA segments that encode peptide antigens from about 8 to about 50 amino acids in length, or more preferably, from about 8 to about 30 amino acids in length, or even more preferably, from about 8 to about 20 amino acids in length are contemplated to be particularly useful. Such peptide epitopes may be amino acid sequences which comprise contiguous amino acid sequences from SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6, SEQ ID NO:8, SEQ ID NO:10, SEQ ID NO:12, SEQ ID NO:14, SEQ ID NO:16, SEQ ID NO:18, SEQ ID NO:20, SEQ ID NO:22, SEQ ID NO:24, SEQ ID NO:26, SEQ ID NO:28, SEQ ID NO:30, SEQ ID NO:32, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:38, SEQ ID NO:40, SEQ ID NO:42, SEQ ID NO:44, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:50 and SEQ ID NO: 63.
2.4 Cry Transgenes and Transgenic Plants Expressing Cry Polypeptides
In yet another aspect, the present invention provides methods for producing a transgenic plant which expresses a nucleic acid segment encoding the novel polypeptides and endotoxins of the present invention. The process of producing transgenic plants is well-known in the art. In general, the method comprises transforming a suitable host cell with a DNA segment which contains a promoter operatively linked to a coding region that encodes one or more CryET31, CryET40, CryET43, CryET44, CryET45, CryET46, CryET47, CryET49, CryET51, CryET52, CryET53, CryET54, CryET55, CryET56, CryET57, CryET59, CryET60, CryET61, CryET62, CryET63, CryET64, CryET66, CryET67, CryET68, CryET72, CryET73, and CryET83 polypeptides. Such a coding region is generally operatively linked to a transcription-terminating region, whereby the promoter is capable of driving the transcription of the coding region in the cell, and hence providing the cell the ability to produce the polypeptide in vivo. Alternatively, in instances where it is desirable to control, regulate, or decrease the amount of a particular recombinant crystal protein expressed in a particular transgenic cell, the invention also provides for the expression of crystal protein antisense mRNA. The use of antisense mRNA as a means of controlling or decreasing the amount of a given protein of interest in a cell is well-known in the art.
Another aspect of the invention comprises transgenic plants which express a gene or gene segment encoding one or more of the novel polypeptide compositions disclosed herein. As used herein, the term xe2x80x9ctransgenic plantxe2x80x9d is intended to refer to a plant that has incorporated DNA sequences, including but not limited to genes which are perhaps not normally present, DNA sequences not normally transcribed into RNA or translated into a protein (xe2x80x9cexpressedxe2x80x9d), or any other genes or DNA sequences which one desires to introduce into the non-transformed plant, such as genes which may normally be present in the non-transformed plant but which one desires to either genetically engineer or to have altered expression.
It is contemplated that in some instances either the nuclear or plastidic genome, or both, of a transgenic plant of the present invention will have been augmented through the stable introduction of one or more cryET31, cryET40, cryET43, cryET44, cryET45, cryET46, cryET47, cryET49, cryET51, cryET52, cryET53, cryET54, cryET55, cryET56, cryET57, cryET59, cryET60, cryET61, cryET62, cryET63, cryET64, cryET66, cryET67, cryET68, cryET72, cryET73, and cryET83 transgenes, either native, synthetically modified, or mutated. In some instances, more than one transgene will be incorporated into one or more genomes of the transformed host plant cell. Such is the case when more than one crystal protein-encoding DNA segment is incorporated into the genome of such a plant. In certain situations, it may be desirable to have one, two, three, four, or even more B. thuringiensis crystal proteins (either native or recombinantly-engineered) incorporated and stably expressed in the transformed transgenic plant.
A preferred gene which may be introduced includes, for example, a crystal protein-encoding DNA sequence from bacterial origin, and particularly one or more of those described herein which are obtained from Bacillus spp. Highly preferred nucleic acid sequences are those obtained from B. thuringiensis, or any of those sequences which have been genetically engineered to decrease or increase the insecticidal activity of the crystal protein in such a transformed host cell.
Means for transforming a plant cell and the preparation of a transgenic cell line are well-known in the art, and are discussed herein. Vectors, plasmids, cosmids, YACs (yeast artificial chromosomes) and DNA segments for use in transforming such cells will, of course, generally comprise either the operons, genes, or gene-derived sequences of the present invention, either native, or synthetically-derived, and particularly those encoding the disclosed crystal proteins. These DNA constructs can further include structures such as promoters, enhancers, polylinkers, or even gene sequences which have positively- or negatively-regulating activity upon the particular genes of interest as desired. The DNA segment or gene may encode either a native or modified crystal protein, which will be expressed in the resultant recombinant cells, and/or which will impart an improved phenotype to the regenerated plant.
Such transgenic plants may be desirable for increasing the insecticidal resistance of a monocotyledonous or dicotyledonous plant, by incorporating into such a plant, a transgenic DNA segment encoding one or more CryET31, CryET40, CryET43, CryET44, CryET45, CryET46, CryET47, CryET49, CryET51, CryET52, CryET53, CryET54, CryET55, CryET56, CryET57, CryET59, CryET60, CryET61, CryET62, CryET63, CryET64, CryET66, CryET67, CryET68, CryET72, CryET73, and CryET83 polypeptides which are toxic to a lepidopteran insect. Particularly preferred plants include turf grasses, kapok, sorghum, cotton, corn, soybeans, oats, rye, wheat, flax, tobacco, rice, tomatoes, potatoes, or other vegetables, ornamental plants, fruit trees, and the like.
In a related aspect, the present invention also encompasses a seed produced by the transformed plant, a progeny from such seed, and a seed produced by the progeny of the original transgenic plant, produced in accordance with the above process. Such progeny and seeds will have a crystal protein-encoding transgene stably incorporated into their genome, and such progeny plants will inherit the traits afforded by the introduction of a stable transgene in Mendelian fashion. All such transgenic plants having incorporated into their genome transgenic DNA segments encoding one or more CryET31, CryET40, CryET43, CryET44, CryET45, CryET46, CryET47, CryET49, CryET51, CryET52, CryET53, CryET54, CryET55, CryET56, CryET57, CryET59, CryET60, CryET61, CryET62, CryET63, CryET64, CryET66, CryET67, CryET68, CryET72, CryET73, and CryET83 crystal proteins or polypeptides are aspects of this invention. As well-known to those of skill in the art, a progeny of a plant is understood to mean any offspring or any descendant from such a plant, but in this case means any offspring or any descendant which also contains the transgene.
2.5 Site-specific Mutagenesis
Site-specific mutagenesis is a technique useful in the preparation of individual peptides, or biologically functional equivalent proteins or peptides, through specific mutagenesis of the underlying DNA. The technique further provides a ready ability to prepare and test sequence variants, for example, incorporating one or more of the foregoing considerations, by introducing one or more nucleotide sequence changes into the DNA. The technique of site-specific mutagenesis is well known in the art, as exemplified by various publications.
In general, site-directed mutagenesis in accordance herewith is performed by first obtaining a single-stranded vector or melting apart of two strands of a double stranded vector which includes within its sequence a DNA sequence which encodes the desired peptide. An oligonucleotide primer bearing the desired mutated sequence is prepared, generally synthetically. This primer is then annealed with the single-stranded vector, and subjected to DNA polymerizing enzymes such as E. coli polymerase I Klenow fragment, in order to complete the synthesis of the mutation-bearing strand. Thus, a heteroduplex is formed wherein one strand encodes the original non-mutated sequence and the second strand bears the desired mutation. This heteroduplex vector is then used to transform appropriate cells, such as E. coli cells, and clones are selected which include recombinant vectors bearing the mutated sequence arrangement.
The preparation of sequence variants of the endotoxin-encoding nucleic acid segments using site-directed mutagenesis is provided as a means of producing potentially useful species and is not meant to be limiting as there are other ways in which sequence variants of peptides and the DNA sequences encoding them may be obtained. For example, recombinant vectors encoding the desired peptide sequence may be treated with mutagenic agents, such as hydroxylamine, to obtain sequence variants.
2.6 Antibody Compositions and Methods of Making
In particular embodiments, the inventors contemplate the use of antibodies, either monoclonal (mAbs) or polyclonal which bind to one or more of the polypeptides disclosed herein. Means for preparing and characterizing antibodies are well known in the art (See, e.g., Harlow and Lane, 1988; incorporated herein by reference). mAbs may be readily prepared through use of well-known techniques, such as those exemplified in U.S. Pat. No. 4,196,265, incorporated herein by reference.
2.7 Elisas and Immunoprecipitation
ELISAs may be used in conjunction with the invention. Many different protocols exist for performing ELISAs. These are well known to those of ordinary skill in the art. Examples of basic ELISA protocols may be found in any standard molecular biology laboratory manual (e.g. Sambrook, Fritsch, and Maniatis, eds. Molecular cloning: a laboratory manual. Cold Spring Harbor, N.Y.: Cold Spring Harbor Laboratory, 1989).
2.8 Western Blots
The compositions of the present invention will find great use in immunoblot or western blot analysis. Methods of performing immunoblot and western blot analysis are well known to those of skill in the are (see Sambrook, et al, ibid). Immunologically-based detection methods for use in conjunction with Western blotting include enzymatically-, radiolabel-, or fluorescently-tagged secondary antibodies against the toxin moiety are considered to be of particular use in this regard.
2.9 Crystal Protein Screening and Detection Kits
The present invention contemplates methods and kits for screening samples suspected of containing crystal protein polypeptides or crystal protein-related polypeptides, or cells producing such polypeptides. A kit may contain one or more antibodies of the present invention, and may also contain reagent(s) for detecting an interaction between a sample and an antibody of the present invention. The provided reagent(s) can be radio-, fluorescently- or enzymatically-labeled or even epitope or ligand tagged. The kit can contain a known radiolabeled agent capable of binding or interacting with a nucleic acid or antibody of the present invention.
The reagent(s) of the kit can be provided as a liquid solution, attached to a solid support or as a dried powder. Preferably, when the reagent(s) are provided in a liquid solution, the liquid solution is an aqueous solution. Preferably, when the reagent(s) provided are attached to a solid support, the solid support can be chromatograph media, a test plate having a plurality of wells, or a microscope slide. When the reagent(s) provided are a dry powder, the powder can be reconstituted by the addition of a suitable solvent, that may be provided.
In still further embodiments, the present invention concerns immunodetection methods and associated kits. It is proposed that the crystal proteins or peptides of the present invention may be employed to detect antibodies having reactivity therewith, or, alternatively, antibodies prepared in accordance with the present invention, may be employed to detect crystal proteins or crystal protein-related epitope-containing peptides. In general, these methods will include first obtaining a sample suspected of containing such a protein, peptide or antibody, contacting the sample with an antibody or peptide in accordance with the present invention, as the case may be, under conditions effective to allow the formation of an immunocomplex, and then detecting the presence of the immunocomplex.
In general, the detection of immunocomplex formation is quite well known in the art and may be achieved through the application of numerous approaches. For example, the present invention contemplates the application of ELISA, RIA, immunoblot (e.g., dot blot), indirect immunofluorescence techniques and the like. One may find additional advantages through the use of a secondary binding ligand such as a second antibody or a biotin/avidin ligand binding arrangement, as is known in the art.
For assaying purposes, it is proposed that virtually any sample suspected of comprising either a crystal protein or peptide or a crystal protein-related peptide or antibody sought to be detected, as the case may be, may be employed. It is contemplated that such embodiments may have application in the titering of antigen or antibody samples, in the selection of hybridomas, and the like. In related embodiments, the present invention contemplates the preparation of kits that may be employed to detect the presence of crystal proteins or related peptides and/or antibodies in a sample. Samples may include cells, cell supernatants, cell suspensions, cell extracts, enzyme fractions, protein extracts, or other cell-free compositions suspected of containing crystal proteins or peptides.
Generally speaking, kits in accordance with the present invention will include a suitable crystal protein, peptide or an antibody directed against such a protein or peptide, together with an immunodetection reagent and a means for containing the antibody or antigen and reagent. The immunodetection reagent will typically comprise a label associated with the antibody or antigen, or associated with a secondary binding ligand. Exemplary ligands might include a secondary antibody directed against the first antibody or antigen or a biotin or avidin (or streptavidin) ligand having an associated label. Of course, as noted above, a number of exemplary labels are known in the art and all such labels may be employed in connection with the present invention.
The container will generally include a vial into which the antibody, antigen or detection reagent may be placed, and preferably suitably aliquotted. The kits of the present invention will also typically include a means for containing the antibody, antigen, and reagent containers in close confinement for commercial sale. Such containers may include injection or blow-molded plastic containers into which the desired vials are retained.
2.10 Epitopic Core Sequences
The present invention is also directed to protein or peptide compositions, free from total cells and other peptides, which comprise a purified protein or peptide which incorporates an epitope that is immunologically cross-reactive with one or more anti-crystal protein antibodies. In particular, the invention concerns epitopic core sequences derived from Cry proteins or peptides.
As used herein, the term xe2x80x9cincorporating an epitope(s) that is immunologically cross-reactive with one or more anti-crystal protein antibodiesxe2x80x9d is intended to refer to a peptide or protein antigen which includes a primary, secondary or tertiary structure similar to an epitope located within a crystal protein or polypeptide. The level of similarity will generally be to such a degree that monoclonal or polyclonal antibodies directed against the crystal protein or polypeptide will also bind to, react with, or otherwise recognize, the cross-reactive peptide or protein antigen. Various immunoassay methods may be employed in conjunction with such antibodies, such as, for example, Western blotting, ELISA, RIA, and the like, all of which are known to those of skill in the art. The identification of Cry immunodominant epitopes, and/or their functional equivalents, suitable for use in vaccines is a relatively straightforward matter (e.g. U.S. Pat. No. 4,554,101; Jameson and Wolf, 1988; Wolf et al., 1988; U.S. Pat. No. 4,554,101). The amino acid sequence of these xe2x80x9cepitopic core sequencesxe2x80x9d may then be readily incorporated into peptides, either through the application of peptide synthesis or recombinant technology.
Preferred peptides for use in accordance with the present invention will generally be on the order of about 8 to about 20 amino acids in length, and more preferably about 8 to about 15 amino acids in length. It is proposed that particular advantages of the present invention may be realized through the preparation of synthetic peptides which include modified and/or extended epitopic/immunogenic core sequences which result in a xe2x80x9cuniversalxe2x80x9d epitopic peptide directed to crystal proteins, and in particular CryET31, CryET40, CryET43, CryET44, CryET45, CryET46, CryET47, CryET49, CryET51, CryET52, CryET53, CryET54, CryET55, CryET56, CryET57, CryET59, CryET60, CryET61, CryET62, CryET63, CryET64, CryET66, CryET67, CryET68, CryET72, CryET73, CryET83 and related sequences. These epitopic core sequences are identified herein in particular aspects as hydrophilic regions of the particular polypeptide antigen.
Computerized peptide sequence analysis programs (e.g., DNAStar(copyright) software, DNAStar, Inc., Madison, Wis.) may also be useful in designing synthetic peptides in accordance with the present disclosure.
Syntheses of epitopic sequences, or peptides which include an antigenic epitope within their sequence, are readily achieved using conventional synthetic techniques such as the solid phase method (e.g., through the use of commercially available peptide synthesizer such as an Applied Biosystems Model 430A Peptide Synthesizer).
2.11 Biological Functional Equivalents
Modification and changes may be made in the structure of the peptides of the present invention and DNA segments which encode them and still obtain a functional molecule that encodes a protein or peptide with desirable characteristics. The following is a discussion based upon changing the amino acids of a protein to create an equivalent, or even an improved, second-generation molecule. In particular embodiments of the invention, mutated crystal proteins are contemplated to be useful for increasing the insecticidal activity of the protein, and consequently increasing the insecticidal activity and/or expression of the recombinant transgene in a plant cell. The amino acid changes may be achieved by changing the codons of the DNA sequence, according to the codons given in Table 1.
For example, certain amino acids may be substituted for other amino acids in a protein structure without appreciable loss of interactive binding capacity with structures such as, for example, antigen-binding regions of antibodies or binding sites on substrate molecules. Since it is the interactive capacity and nature of a protein that defines that protein""s biological functional activity, certain amino acid sequence substitutions can be made in a protein sequence, and, of course, its underlying DNA coding sequence, and nevertheless obtain a protein with like properties. It is thus contemplated by the inventors that various changes may be made in the peptide sequences of the disclosed compositions, or corresponding DNA sequences which encode said peptides without appreciable loss of their biological utility or activity.
In making such changes, the hydropathic index of amino acids may be considered. The importance of the hydropathic amino acid index in conferring interactive biologic function on a protein is generally understood in the art (Kyte and Doolittle, 1982, incorporate herein by reference). It is accepted that the relative hydropathic character of the amino acid contributes to the secondary structure of the resultant protein, which in turn defines the interaction of the protein with other molecules, for example, enzymes, substrates, receptors, DNA, antibodies, antigens, and the like.
Each amino acid has been assigned a hydropathic index on the basis of their hydrophobicity and charge characteristics (Kyte and Doolittle, 1982), these are: isoleucine (+4.5); valine (+4.2); leucine (+3.8); phenylalanine (+2.8); cysteine/cystine (+2.5); methionine (+1.9); alanine (+1.8); glycine (xe2x88x920.4); threonine (xe2x88x920.7); serine (xe2x88x920.8); tryptophan (xe2x88x920.9); tyrosine (xe2x88x921.3); proline (xe2x88x921.6); histidine (xe2x88x923.2); glutamate (xe2x88x923.5); glutamine (xe2x88x923.5); aspartate (xe2x88x923.5); asparagine (xe2x88x923.5); lysine (xe2x88x923.9); and arginine (xe2x88x924.5).
It is known in the art that certain amino acids may be substituted by other amino acids having a similar hydropathic index or score and still result in a protein with similar biological activity, i.e., still obtain a biological functionally equivalent protein. In making such changes, the substitution of amino acids whose hydropathic indices are within xc2x12 is preferred, those which are within +1 are particularly preferred, and those within xc2x10.5 are even more particularly preferred.
It is also understood in the art that the substitution of like amino acids can be made effectively on the basis of hydrophilicity. U.S. Pat. No. 4,554,101, incorporated herein by reference, states that the greatest local average hydrophilicity of a protein, as governed by the hydrophilicity of its adjacent amino acids, correlates with a biological property of the protein.
As detailed in U.S. Pat. No. 4,554,101, the following hydrophilicity values have been assigned to amino acid residues: arginine (+3.0); lysine (+3.0); aspartate (+3.0xc2x11); glutamate (+3.0xc2x11); serine (+0.3); asparagine (+0.2); glutamine (+0.2); glycine (0); threonine (xe2x88x920.4); proline (xe2x88x920.5xc2x11); alanine (xe2x88x920.5); histidine (xe2x88x920.5); cysteine (xe2x88x921.0); methionine (xe2x88x921.3); valine (xe2x88x921.5); leucine (xe2x88x921.8); isoleucine (xe2x88x921.8); tyrosine (xe2x88x922.3); phenylalanine (xe2x88x922.5); tryptophan (xe2x88x923.4).
It is understood that an amino acid can be substituted for another having a similar hydrophilicity value and still obtain a biologically equivalent, and in particular, an immunologically equivalent protein. In such changes, the substitution of amino acids whose hydrophilicity values are within xc2x12 is preferred, those which are within xc2x11 are particularly preferred, and those within xc2x10.5 are even more particularly preferred.
As outlined above, amino acid substitutions are generally therefore based on the relative similarity of the amino acid side-chain substituents, for example, their hydrophobicity, hydrophilicity, charge, size, and the like. Exemplary substitutions which take various of the foregoing characteristics into consideration are well known to those of skill in the art and include: arginine and lysine; glutamate and aspartate; serine and threonine; glutamine and asparagine; and valine, leucine and isoleucine.
2.12 Insecticidal Compositions and Methods of Use
The inventors contemplate that the crystal protein compositions disclosed herein will find particular utility as insecticides for topical and/or systemic application to field crops, grasses, fruits and vegetables, and ornamental plants. In a preferred embodiment, the bioinsecticide composition comprises an oil flowable suspension of bacterial cells which expresses a novel crystal protein disclosed herein. Preferably the cells are B. thuringiensis NRRL B-21921, NRRL B-21922, NRRL B-21923, NRRL B-21924, NRRL B-21925, NRRL B-21926, NRRL B-21927, NRRL B-21928, NRRL B-21929, NRRL B-21930, NRRL B-21931, NRRL B-21932, NRRL B-21933, NRRL B-21934, NRRL B-21935, NRRL B-21936, NRRL B-21937, NRRL B-21938, NRRL B-21939, NRRL B-21940, NRRL B-21941, NRRL B-21942, NRRL B-21943, and NRRL B-21944, however, any such bacterial host cell expressing the novel nucleic acid segments disclosed herein and producing a crystal protein is contemplated to be useful, such as B. thuringiensis, B. megaterium, B. subtilis, E. coli, or Pseudomonas spp.
In another important embodiment, the bioinsecticide composition comprises a water dispersible granule. This granule comprises bacterial cells which expresses a novel crystal protein disclosed herein. Preferred bacterial cells are B. thuringiensis NRRL B-21921, NRRL B-21922, NRRL B-21923, NRRL B-21924, NRRL B-21925, NRRL B-21926, NRRL B-21927, NRRL B-21928, NRRL B-21929, NRRL B-21930, NRRL B-21931, NRRL B-21932, NRRL B-21933, NRRL B-21934, NRRL B-21935, NRRL B-21936, NRRL B-21937, NRRL B-21938, NRRL B-21939, NRRL B-21940, NRRL B-21941, NRRL B-21942, NRRL B-21943, and NRRL B-21944, however, bacteria such as B. thuringiensis, B. megaterium, B. subtilis, E. coli, or Pseudomonas spp. cells transformed with a DNA segment disclosed herein and expressing the crystal protein are also contemplated to be useful.
In a third important embodiment, the bioinsecticide composition comprises a wettable powder, dust, pellet, or collodial concentrate. This powder comprises bacterial cells which expresses a novel crystal protein disclosed herein. Preferred bacterial cells are B. thuringiensis NRRL B-21921, NRRL B-21922, NRRL B-21923, NRRL B-21924, NRRL B-21925, NRRL B-21926, NRRL B-21927, NRRL B-21928, NRRL B-21929, NRRL B-21930, NRRL B-21931, NRRL B-21932, NRRL B-21933, NRRL B-21934, NRRL B-21935, NRRL B-21936, NRRL B-21937, NRRL B-21938, NRRL B-21939, NRRL B-21940, NRRL B-21941, NRRL B-21942, NRRL B-21943, and NRRL B-21944 cells, however, bacteria such as B. thuringiensis, B. megaterium, B. subtilis, E. coli, or Pseudomonas spp. cells transformed with a DNA segment disclosed herein and expressing the crystal protein are also contemplated to be useful. Such dry forms of the insecticidal compositions may be formulated to dissolve immediately upon wetting, or alternatively, dissolve in a controlled-release, sustained-release, or other time-dependent manner.
In a fourth important embodiment, the bioinsecticide composition comprises an aqueous suspension of bacterial cells such as those described above which express the crystal protein. Such aqueous suspensions may be provided as a concentrated stock solution which is diluted prior to application, or alternatively, as a diluted solution ready-to-apply.
For these methods involving application of bacterial cells, the cellular host containing the crystal protein gene(s) may be grown in any convenient nutrient medium, where the DNA construct provides a selective advantage, providing for a selective medium so that substantially all or all of the cells retain the B. thuringiensis gene. These cells may then be harvested in accordance with conventional ways. Alternatively, the cells can be treated prior to harvesting.
When the insecticidal compositions comprise intact B. thuringiensis cells expressing the protein of interest, such bacteria may be formulated in a variety of ways. They may be employed as wettable powders, granules or dusts, by mixing with various diluents, inert materials, such as inorganic minerals (phyllosilicates, carbonates, sulfates, phosphates, and the like) or botanical materials (powdered corncobs, rice hulls, walnut shells, and the like). The formulations may include spreader-sticker adjuvants, stabilizing agents, other pesticidal additives, or surfactants. Liquid formulations may be aqueous-based or non-aqueous and employed as foams, suspensions, emulsifiable concentrates, or the like. The ingredients may include rheological agents, surfactants, emulsifiers, dispersants, or polymers.
Alternatively, the novel insecticidal polypeptides may be prepared by native or recombinant bacterial expression systems in vitro and isolated for subsequent field application. Such protein may be either in crude cell lysates, suspensions, colloids, etc., or alternatively may be purified, refined, buffered, and/or further processed, before formulating in an active biocidal formulation. Likewise, under certain circumstances, it may be desirable to isolate crystals and/or spores from bacterial cultures expressing the crystal protein and apply solutions, suspensions, or collodial preparations of such crystals and/or spores as the active bioinsecticidal composition.
Regardless of the method of application, the amount of the active component(s) is applied at an insecticidally-effective amount, which will vary depending on such factors as, for example, the specific coleopteran insects to be controlled, the specific plant or crop to be treated, the environmental conditions, and the method, rate, and quantity of application of the insecticidally-active composition.
The insecticide compositions described may be made by formulating either the bacterial cell, crystal and/or spore suspension, or isolated protein component with the desired agriculturally-acceptable carrier. The compositions may be formulated prior to administration in an appropriate means such as lyophilized, freeze-dried, dessicated, or in an aqueous carrier, medium or suitable diluent, such as saline or other buffer. The formulated compositions may be in the form of a dust or granular material, or a suspension in oil (vegetable or mineral), or water or oil/water emulsions, or as a wettable powder, or in combination with any other carrier material suitable for agricultural application. Suitable agricultural carriers can be solid or liquid and are well known in the art. The term xe2x80x9cagriculturally-acceptable carrierxe2x80x9d covers all adjuvants, E. coli, inert components, dispersants, surfactants, tackifiers, binders, etc. that are ordinarily used in insecticide formulation technology; these are well known to those skilled in insecticide formulation. The formulations may be mixed with one or more solid or liquid adjuvants and prepared by various means, E. coli, by homogeneously mixing, blending and/or grinding the insecticidal composition with suitable adjuvants using conventional formulation techniques.
The insecticidal compositions of this invention are applied to the environment of the target lepidopteran insect, typically onto the foliage of the plant or crop to be protected, by conventional methods, preferably by spraying. The strength and duration of insecticidal application will be set with regard to conditions specific to the particular pest(s), crop(s) to be treated and particular environmental conditions. The proportional ratio of active ingredient to carrier will naturally depend on the chemical nature, solubility, and stability of the insecticidal composition, as well as the particular formulation contemplated.
Other application techniques, including dusting, sprinkling, soaking, soil injection, seed coating, seedling coating, spraying, aerating, misting, atomizing, and the like, are also feasible and may be required under certain circumstances such as e.g., insects that cause root or stalk infestation, or for application to delicate vegetation or ornamental plants. These application procedures are also well-known to those of skill in the art.
The insecticidal composition of the invention may be employed in the method of the invention singly or in combination with other compounds, including and not limited to other pesticides. The method of the invention may also be used in conjunction with other treatments such as surfactants, detergents, polymers or time-release formulations. The insecticidal compositions of the present invention may be formulated for either systemic or topical use.
The concentration of insecticidal composition which is used for environmental, systemic, or foliar application will vary widely depending upon the nature of the particular formulation, means of application, environmental conditions, and degree of biocidal activity. Typically, the bioinsecticidal composition will be present in the applied formulation at a concentration of at least about 1% by weight and may be up to and including about 99% by weight. Dry formulations of the polypeptide compositions may be from about 1% to about 99% or more by weight of the protein composition, while liquid formulations may generally comprise from about 1% to about 99% or more of the active ingredient by weight. Formulations which comprise intact bacterial cells will generally contain from about 104 to about 107 cells/mg.
The insecticidal formulation may be administered to a particular plant or target area in one or more applications as needed, with a typical field application rate per hectare ranging on the order of from about 50 g to about 500 g of active ingredient, or of from about 500 g to about 1000 g, or of from about 1000 g to about 5000 g or more of active ingredient.
5.1 Some Advantages of the Invention
The use of B. thuringiensis insecticidal crystal protein genes for in planta production of insecticidal proteins, thereby conferring insect resistance on important agronomic plants, is rapidly gaining commercial acceptance in the United States and abroad. The need for new insecticidal traits does not diminish, however, with the successful deployment of a handful of cry genes in plants. Concerns over the potential for insect resistance development, for instance, makes it imperative that an arsenal of insecticidal proteins (i.e. cry genes) be assembled to provide the genetic material necessary for tomorrow""s insecticidal traits. In addition, transgenic plants producing a B. thuringiensis Cry protein may still be susceptible to damage from secondary insect pests, thus prompting the search for additional Cry proteins with improved efficacy towards these pests. The B. thuringiensis crystal proteins of the present invention represent a diverse collection of insecticidal proteins, including several that are toxic towards a lepidopteran colony exhibiting resistance to certain types of Cry1 proteins. Bioassays against a wide range of lepidopteran pests confirm that these proteins possess insecticidal activity and, furthermore, that these proteins vary in efficacy against this array of target insects. This variation in the spectrum of insects affected by the toxin proteins suggests differing modes of action that may be important for future insect resistance management strategies. In planta expression of the cry genes of the present invention can confer insect resistance to the host plant as has been demonstrated for other cry genes from B. thuringiensis. 
5.2 Probes and Primers
In another aspect, DNA sequence information provided by the invention allows for the preparation of relatively short DNA (or RNA) sequences having the ability to specifically hybridize to gene sequences of the selected polynucleotides disclosed herein. In these aspects, nucleic acid probes of an appropriate length are prepared based on a consideration of a selected crystal protein gene sequence, e.g., a sequence such as that shown in SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:9, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62. The ability of such DNAs and nucleic acid probes to specifically hybridize to a crystal protein-encoding gene sequence lends them particular utility in a variety of embodiments. Most importantly, the probes may be used in a variety of assays for detecting the presence of complementary sequences in a given sample.
In certain embodiments, it is advantageous to use oligonucleotide primers. The sequence of such primers is designed using a polynucleotide of the present invention for use in detecting, amplifying or mutating a defined segment of a crystal protein gene from B. thuringiensis using PCR(trademark) technology. Segments of related crystal protein genes from other species may also be amplified by PCR(trademark) using such primers.
To provide certain of the advantages in accordance with the present invention, a preferred nucleic acid sequence employed for hybridization studies or assays includes sequences that are complementary to at least a 14 to 30 or so long nucleotide stretch of a crystal protein-encoding sequence, such as that shown in SEQ ID NO:1, SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, SEQ ID NO:9, SEQ ID NO:11, SEQ ID NO:13, SEQ ID NO:15, SEQ ID NO:17, SEQ ID NO:19, SEQ ID NO:21, SEQ ID NO:23, SEQ ID NO:25, SEQ ID NO:27, SEQ ID NO:29, SEQ ID NO:31, SEQ ID NO:33, SEQ ID NO:35, SEQ ID NO:37, SEQ ID NO:39, SEQ ID NO:41, SEQ ID NO:43, SEQ ID NO:45, SEQ ID NO:47, SEQ ID NO:49 and SEQ ID NO:62. A size of at least about 14 or so nucleotides in length helps to ensure that the fragment will be of sufficient length to form a duplex molecule that is both stable and selective. Molecules having complementary sequences over stretches greater than about 14 or so bases in length are generally preferred, though, in order to increase stability and selectivity of the hybrid, and thereby improve the quality and degree of specific hybrid molecules obtained. One will generally prefer to design nucleic acid molecules having gene-complementary stretches of about 14 to about 20 or so nucleotides, or even longer where desired. Such fragments may be readily prepared by, for example, directly synthesizing the fragment by chemical means, by application of nucleic acid reproduction technology, such as the PCR(trademark) technology of U.S. Pat. Nos. 4,683,195, and 4,683,202, herein incorporated by reference, or by excising selected DNA fragments from recombinant plasmids containing appropriate inserts and suitable restriction sites.
5.3 Expression Vectors
The present invention contemplates an expression vector comprising a polynucleotide of the present invention. Thus, in one embodiment an expression vector is an isolated and purified DNA molecule comprising a promoter operatively linked to an coding region that encodes a polypeptide of the present invention, which coding region is operatively linked to a transcription-terminating region, whereby the promoter drives the transcription of the coding region.
As used herein, the term xe2x80x9coperatively linkedxe2x80x9d means that a promoter is connected to an coding region in such a way that the transcription of that coding region is controlled and regulated by that promoter. Means for operatively linking a promoter to a coding region are well known in the art.
In a preferred embodiment, the recombinant expression of DNAs encoding the crystal proteins of the present invention is preferable in a Bacillus host cell. Preferred host cells include B. thuringiensis, B. megaterium, B. subtilis, and related bacilli, with B. thuringiensis host cells being highly preferred. Promoters that function in bacteria are well-known in the art. An exemplary and preferred promoter for the Bacillus crystal proteins include any of the known crystal protein gene promoters, including the cryET31, cryET40, cryET43, cryET44, cryET45, cryET46, cryET47, cryET49, cryET51, cryET52, cryET53, cryET54, cryET55, cryET56, cryET57, cryET59, cryET60, cryET61, cryET62, cryET63, cryET64, cryET66, cryET67, cryET68, cryET72, cryET73, and cryET83 gene promoters. Alternatively, mutagenized or recombinant crystal protein-encoding gene promoters may be engineered by the hand of man and used to promote expression of the novel gene segments disclosed herein.
In an alternate embodiment, the recombinant expression of DNAs encoding the crystal proteins of the present invention is performed using a transformed Gram-negative bacterium such as an E. coli or Pseudomonas spp. host cell. Promoters which function in high-level expression of target polypeptides in E. Coli and other Gram-negative host cells are also well-known in the art.
Where an expression vector of the present invention is to be used to transform a plant, a promoter is selected that has the ability to drive expression in plants. Promoters that function in plants are also well known in the art. Useful in expressing the polypeptide in plants are promoters that are inducible, viral, synthetic, constitutive as described (Poszkowski et al., 1989; Odell et al., 1985), and temporally regulated, spatially regulated, and spatio-temporally regulated (Chau et al., 1989).
A promoter is also selected for its ability to direct the transformed plant cell""s or transgenic plant""s transcriptional activity to the coding region. Structural genes can be driven by a variety of promoters in plant tissues. Promoters can be near-constitutive, such as the CaMV 35S promoter, or tissue-specific or developmentally specific promoters affecting dicots or monocots.
Where the promoter is a near-constitutive promoter such as CaMV 35S, increases in polypeptide expression are found in a variety of transformed plant tissues (e.g., callus, leaf, seed and root). Alternatively, the effects of transformation can be directed to specific plant tissues by using plant integrating vectors containing a tissue-specific promoter.
An exemplary tissue-specific promoter is the lectin promoter, which is specific for seed tissue. The Lectin protein in soybean seeds is encoded by a single gene (Le1) that is only expressed during seed maturation and accounts for about 2 to about 5% of total seed mRNA. The lectin gene and seed-specific promoter have been fully characterized and used to direct seed specific expression in transgenic tobacco plants (Vodkin et al., 1983; Lindstrom et al., 1990.)
An expression vector containing a coding region that encodes a polypeptide of interest is engineered to be under control of the lectin promoter and that vector is introduced into plants using, for example, a protoplast transformation method (Dhir et al., 1991). The expression of the polypeptide is directed specifically to the seeds of the transgenic plant.
A transgenic plant of the present invention produced from a plant cell transformed with a tissue specific promoter can be crossed with a second transgenic plant developed from a plant cell transformed with a different tissue specific promoter to produce a hybrid transgenic plant that shows the effects of transformation in more than one specific tissue.
Exemplary tissue-specific promoters are corn sucrose synthetase 1 (Yang et al., 1990), corn alcohol dehydrogenase 1 (Vogel et al., 1989), corn light harvesting complex (Simpson, 1986), corn heat shock protein (Odell et al., 1985), pea small subunit RuBP carboxylase (Poulsen et al., 1986; Cashmore et al., 1983), Ti plasmid mannopine synthase (Langridge et al., 1989), Ti plasmid nopaline synthase (Langridge et al, 1989), petunia chalcone isomerase (Van Tunen et al., 1988), bean glycine rich protein 1 (Keller et al., 1989), CaMV 35s transcript (Odell et al, 1985) and Potato patatin (Wenzler et al., 1989). Preferred promoters include a cauliflower mosaic virus (CaMV 35S) promoter, a S-E9 small subunit RuBP carboxylase promoter, a rice actin promoter, a maize histone promoter, a fused CaMV 35S-Arabidopsis histone promoter, a CaMV 35S promoter, a CaMV 19S promoter, a nos promoter, an Adh promoter, an actin promoter, a histone promoter, a ribulose bisphosphate carboxylase promoter, an R-allele promoter, a root cell promoter, an xcex1-tubulin promoter, an ABA-inducible promoter, a turgor-inducible promoter, a rbcS promoter, a corn sucrose synthetase 1 promoter, a corn alcohol dehydrogenase 1 promoter, a corn light harvesting complex promoter, a corn heat shock protein promoter, a pea small subunit RuBP carboxylase promoter, a Ti plasmid mannopine synthase promoter, a Ti plasmid nopaline synthase promoter, a petunia chalcone isomerase promoter, a bean glycine rich protein 1 promoter, a CaMV 35s transcript promoter, a potato patatin promoter, a cab promoter, a PEP-Carboxylase promoter and an S-E9 small subunit RuBP carboxylase promoter.
The choice of which expression vector and ultimately to which promoter a polypeptide coding region is operatively linked depends directly on the functional properties desired, e.g., the location and timing of protein expression, and the host cell to be transformed. These are well known limitations inherent in the art of constructing recombinant DNA molecules. However, a vector useful in practicing the present invention is capable of directing the expression of the polypeptide coding region to which it is operatively linked.
Typical vectors useful for expression of genes in higher plants are well known in the art and include vectors derived from the tumor-inducing (Ti) plasmid of Agrobacterium tumefaciens described (Rogers et al., 1987). However, several other plant integrating vector systems are known to function in plants including pCaMVCN transfer control vector described (Fromm et al., 1985). Plasmid pCaMVCN (available from Pharmacia, Piscataway, N.J.) includes the cauliflower mosaic virus CaMV 35S promoter.
In preferred embodiments, the vector used to express the polypeptide includes a selection marker that is effective in a plant cell, preferably a drug resistance selection marker. One preferred drug resistance marker is the gene whose expression results in kanamycin resistance; i.e., the chimeric gene containing the nopaline synthase promoter, Tn5 neomycin phosphotransferase II (nptII) and nopaline synthase 3xe2x80x2 non-translated region described (Rogers et al., 1988).
RNA polymerase transcribes a coding DNA sequence through a site where polyadenylation occurs. Typically, DNA sequences located a few hundred base pairs downstream of the polyadenylation site serve to terminate transcription. Those DNA sequences are referred to herein as transcription-termination regions. Those regions are required for efficient polyadenylation of transcribed messenger RNA (mRNA).
Means for preparing expression vectors are well known in the art. Expression (transformation vectors) used to transform plants and methods of making those vectors are described in U.S. Pat. Nos. 4,971,908, 4,940,835, 4,769,061 and 4,757,011, the disclosures of which are incorporated herein by reference. Those vectors can be modified to include a coding sequence in accordance with the present invention.
A variety of methods has been developed to operatively link DNA to vectors via complementary cohesive termini or blunt ends. For instance, complementary homopolymer tracts can be added to the DNA segment to be inserted and to the vector DNA. The vector and DNA segment are then joined by hydrogen bonding between the complementary homopolymeric tails to form recombinant DNA molecules.
A coding region that encodes a polypeptide having the ability to confer insecticidal activity to a cell is preferably a CryET31, CryET40, CryET43, CryET44, CryET45, CryET46, CryET47, CryET49, CryET51, CryET52, CryET53, CryET54, CryET55, CryET56, CryET57, CryET59, CryET60, CryET61, CryET62, CryET63, CryET64, CryET66, CryET67, CryET68, CryET72, CryET73, and CryET83 polypeptide-encoding gene.
5.7 Nomenclature of the Novel Polypeptides
The inventors have arbitrarily assigned the designation CryET31, CryET40, CryET43, CryET44, CryET45, CryET46, CryET47, CryET49, CryET51, CryET52, CryET53, CryET54, CryET56, CryET57, CryET59, CryET60, CryET61, CryET62, CryET63, CryET64, CryET66, CryET67, CryET68, CryET72, CryET73, and CryET83 to the polypeptides of this invention. Likewise, the arbitrary designations of cryET31, cryET40, cryET43, cryET44, cryET45, cryET46, cryET47, cryET49, cryET51, cryET52, cryET53, cryET54, cryET56, cryET57, cryET59, cryET60, cryET61, cryET62, cryET63, cryET64, cryET66, cryET67, cryET68, cryET72, cryET73, and cryET83 have been assigned to the novel nucleic acid sequence which encodes these polypeptides, respectively. Formal assignment of gene and protein designations based on the revised nomenclature of crystal protein endotoxins will be assigned by a committee on the nomenclature of B. thuringiensis, formed to systematically classify B. thuringiensis crystal proteins. The inventors contemplate that the arbitrarily assigned designations of the present invention will be superceded by the official nomenclature assigned to these sequences.
5.8 Transformed Host Cells and Transgenic Plants
Methods and compositions for transforming a bacterium, a yeast cell, a plant cell, or an entire plant with one or more expression vectors comprising a crystal protein-encoding gene segment are further aspects of this disclosure. A transgenic bacterium, yeast cell, plant cell or plant derived from such a transformation process or the progeny and seeds from such a transgenic plant are also further embodiments of the invention.
Means for transforming bacteria and yeast cells are well known in the art. Typically, means of transformation are similar to those well known means used to transform other bacteria or yeast such as E. coli or Saccharomyces cerevisiae. Methods for DNA transformation of plant cells include Agrobacterium-mediated plant transformation, protoplast transformation, gene transfer into pollen, injection into reproductive organs, injection into immature embryos and particle bombardment. Each of these methods has distinct advantages and disadvantages. Thus, one particular method of introducing genes into a particular plant strain may not necessarily be the most effective for another plant strain, but it is well known which methods are useful for a particular plant strain.
There are many methods for introducing transforming DNA segments into cells, but not all are suitable for delivering DNA to plant cells. Suitable methods are believed to include virtually any method by which DNA can be introduced into a cell, such as by Agrobacterium infection, direct delivery of DNA such as, for example, by PEG-mediated transformation of protoplasts (Omirulleh et al., 1993), by desiccation/inhibition-mediated DNA uptake, by electroporation, by agitation with silicon carbide fibers, by acceleration of DNA coated particles, etc. In certain embodiments, acceleration methods are preferred and include, for example, microprojectile bombardment and the like.
Technology for introduction of DNA into cells is well-known to those of skill in the art. Four general methods for delivering a gene into cells have been described: (1) chemical methods (Graham and van der Eb, 1973; Zatloukal et al., 1992); (2) physical methods such as microinjection (Capecchi, 1980), electroporation (Wong and Neumann, 1982; Fromm et al., 1985; U.S. Pat. No. 5,384,253) and the gene gun (Johnston and Tang, 1994; Fynan et al., 1993); (3) viral vectors (Clapp, 1993; Lu et al, 1993; Eglitis and Anderson, 1988a; 1988b); and (4) receptor-mediated mechanisms (Curiel et al., 1991; 1992; Wagner et al., 1992).
5.8.3 Agrobacterium-mediated Transfer
Agrobacterium-mediated transfer is a widely applicable system for introducing genes into plant cells because the DNA can be introduced into whole plant tissues, thereby bypassing the need for regeneration of an intact plant from a protoplast. The use of Agrobacterium-mediated plant integrating vectors to introduce DNA into plant cells is well known in the art. See, for example, the methods described (Fraley et al., 1985; Rogers et al., 1987). Further, the integration of the Ti-DNA is a relatively precise process resulting in few rearrangements. The region of DNA to be transferred is defined by the border sequences, and intervening DNA is usually inserted into the plant genome as described (Spielmann et al., 1986; Jorgensen et al., 1987).
Modern Agrobacterium transformation vectors are capable of replication in E. coli as well as Agrobacterium, allowing for convenient manipulations as described (Klee et al., 1985). Moreover, recent technological advances in vectors for Agrobacterium-mediated gene transfer have improved the arrangement of genes and restriction sites in the vectors to facilitate construction of vectors capable of expressing various polypeptide coding genes. The vectors described (Rogers et al., 1987), have convenient multi-linker regions flanked by a promoter and a polyadenylation site for direct expression of inserted polypeptide coding genes and are suitable for present purposes. In addition, Agrobacterium containing both armed and disarmed Ti genes can be used for the transformations. In those plant strains where Agrobacterium-mediated transformation is efficient, it is the method of choice because of the facile and defined nature of the gene transfer.
Agrobacterium-mediated transformation of leaf disks and other tissues such as cotyledons and hypocotyls appears to be limited to plants that Agrobacterium naturally infects. Agrobacterium-mediated transformation is most efficient in dicotyledonous plants. Few monocots appear to be natural hosts for Agrobacterium, although transgenic plants have been produced in asparagus using Agrobacterium vectors as described (Bytebier et al., 1987). Therefore, commercially important cereal grains such as rice, corn, and wheat must usually be transformed using alternative methods. However, as mentioned above, the transformation of asparagus using Agrobacterium can also be achieved (see, for example, Bytebier et al., 1987).
A transgenic plant formed using Agrobacterium transformation methods typically contains a single gene on one chromosome. Such transgenic plants can be referred to as being heterozygous for the added gene. However, inasmuch as use of the word xe2x80x9cheterozygousxe2x80x9d usually implies the presence of a complementary gene at the same locus of the second chromosome of a pair of chromosomes, and there is no such gene in a plant containing one added gene as here, it is believed that a more accurate name for such a plant is an independent segregant, because the added, exogenous gene segregates independently during mitosis and meiosis.
More preferred is a transgenic plant that is homozygous for the added structural gene; i.e., a transgenic plant that contains two added genes, one gene at the same locus on each chromosome of a chromosome pair. A homozygous transgenic plant can be obtained by sexually mating (selfing) an independent segregant transgenic plant that contains a single added gene, germinating some of the seed produced and analyzing the resulting plants produced for enhanced carboxylase activity relative to a control (native, non-transgenic) or an independent segregant transgenic plant.
It is to be understood that two different transgenic plants can also be mated to produce offspring that contain two independently segregating added, exogenous genes. Selfing of appropriate progeny can produce plants that are homozygous for both added, exogenous genes that encode a polypeptide of interest. Back-crossing to a parental plant and out-crossing with a non-transgenic plant are also contemplated.
Transformation of plant protoplasts can be achieved using methods based on calcium phosphate precipitation, polyethylene glycol treatment, electroporation, and combinations of these treatments (see, e.g., Potrykus et al., 1985; Lorz et al., 1985; Fromm et al., 1985; Uchimiya et al., 1986; Callis et al., 1987; Marcotte et al., 1988).
Application of these systems to different plant strains depends upon the ability to regenerate that particular plant strain from protoplasts. Illustrative methods for the regeneration of cereals from protoplasts are described (Fujimura et al., 1985; Toriyama et al., 1986; Yamada et al., 1986; Abdullah et al., 1986).
5.8.4 Other Transformation Methods
Transformation of plant protoplasts can be achieved using methods based on calcium phosphate precipitation, polyethylene glycol treatment, electroporation, and combinations of these treatments (see, e.g., Potrykus et al., 1985; Lorz et al., 1985; Fromm et al., 1985; Uchimiya et al., 1986; Callis et al, 1987; Marcotte et al., 1988).
Illustrative methods for the regeneration of cereals from protoplasts are described (Fujimura et al., 1985; Toriyama et al., 1986; Yamada et al., 1986; Abdullah et al., 1986).
5.8.5 Gene Expression in Plants
Although great progress has been made in recent years with respect to preparation of transgenic plants which express bacterial proteins such as B. thuringiensis crystal proteins, the results of expressing native bacterial genes in plants are often disappointing. In recent years, however, several potential factors have been implicated as responsible in varying degrees for the level of protein expression from a particular coding sequence. For example, scientists now know that maintaining a significant level of a particular mRNA in the cell is indeed a critical factor. Unfortunately, the causes for low steady state levels of mRNA encoding foreign proteins are many. First, full length RNA synthesis may not occur at a high frequency. This could, for example, be caused by the premature termination of RNA during transcription or due to unexpected mRNA processing during transcription. Second, full length RNA may be produced in the plant cell, but then processed (splicing, polyA addition) in the nucleus in a fashion that creates a nonfunctional mRNA. If the RNA is not properly synthesized, terminated and polyadenylated, it cannot move to the cytoplasm for translation. Similarly, in the cytoplasm, if mRNAs have reduced half lives (which are determined by their primary or secondary sequence) inisufficient protein product will be produced. In addition, there is an effect, whose magnitude is uncertain, of translational efficiency on mRNA half-life. In addition, every RNA molecule folds into a particular structure, or perhaps family of structures, which is determined by its sequence. The particular structure of any RNA might lead to greater or lesser stability in the cytoplasm. Structure per se is probably also a determinant of mRNA processing in the nucleus. It is likely that dramatically changing the sequence of an RNA will have a large effect on its folded structure It is likely that structure per se or particular structural features also have a role in determining RNA stability.
To overcome these limitations in foreign gene expression, researchers have identified particular sequences and signals in RNAs that have the potential for having a specific effect on RNA stability. In certain embodiments of the invention, therefore, there is a desire to optimize expression of the disclosed nucleic acid segments in planta. One particular method of doing so, is by alteration of the bacterial gene to remove sequences or motifs which decrease expression in a transformed plant cell. The process of engineering a coding sequence for optimal expression in planta is often referred to as xe2x80x9cplantizingxe2x80x9d a DNA sequence.
Particularly problematic sequences are those which are A+T rich. Unfortunately, since B. thuringiensis has an A+T rich genome, native crystal protein gene sequences must often be modified for optimal expression in a plant. The sequence motif ATTTA (or AUUUA as it appears in RNA) has been implicated as a destabilizing sequence in mammalian cell mRNA (Shaw and Kamen, 1986). Many short lived mRNAs have A+T rich 3xe2x80x2 untranslated regions, and these regions often have the ATTTA sequence, sometimes present in multiple copies or as multimers (e.g., ATTTATTTA . . . ). Shaw and Kamen showed that the transfer of the 3xe2x80x2 end of an unstable mRNA to a stable RNA (globin or VA1) decreased the stable RNA""s half life dramatically. They further showed that a pentamer of ATTTA had a profound destabilizing effect on a stable message, and that this signal could exert its effect whether it was located at the 3xe2x80x2 end or within the coding sequence. However, the number of ATTTA sequences and/or the sequence context in which they occur also appear to be important in determining whether they function as destabilizing sequences. Shaw and Kamen showed that a trimer of ATTTA had much less effect than a pentamer on mRNA stability and a dimer or a monomer had no effect on stability (Shaw and Kamen, 1987). Note that multimers of ATTTA such as a pentamer automatically create an A+T rich region. This was shown to be a cytoplasmic effect, not nuclear. In other unstable mRNAs, the ATTTA sequence may be present in only a single copy, but it is often contained in an A+T rich region. From the animal cell data collected to date, it appears that ATTTA at least in some contexts is important in stability, but it is not yet possible to predict which occurrences of ATTTA are destabiling elements or whether any of these effects are likely to be seen in plants.
Some studies on mRNA degradation in animal cells also indicate that RNA degradation may begin in some cases with nucleolytic attack in A+T rich regions. It is not clear if these cleavages occur at ATTTA sequences. There are also examples of mRNAs that have differential stability depending on the cell type in which they are expressed or on the stage within the cell cycle at which they are expressed. For example, histone mRNAs are stable during DNA synthesis but unstable if DNA synthesis is disrupted. The 3xe2x80x2 end of some histone mRNAs seems to be responsible for this effect (Pandey and Marzluff, 1987). It does not appear to be mediated by ATTTA, nor is it clear what controls the differential stability of this mRNA. Another example is the differential stability of IgG mRNA in B lymphocytes during B cell maturation (Genovese and Milcarek, 1988). A final example is the instability of a mutant xcex2-thallesemic globin mRNA. In bone marrow cells, where this gene is normally expressed, the mutant mRNA is unstable, while the wild-type mRNA is stable. When the mutant gene is expressed in HeLa or L cells in vitro, the mutant mRNA shows no instability (Lim et al., 1988). These examples all provide evidence that mRNA stability can be mediated by cell type or cell cycle specific factors. Furthermore this type of instability is not yet associated with specific sequences. Given these uncertainties, it is not possible to predict which RNAs are likely to be unstable in a given cell. In addition, even the ATTTA motif may act differentially depending on the nature of the cell in which the RNA is present. Shaw and Kamen (1987) have reported that activation of protein kinase C can block degradation mediated by ATTTA.
The addition of a polyadenylate string to the 3xe2x80x2 end is common to most eukaryotic mRNAs, both plant and animal. The currently accepted view of polyA addition is that the nascent transcript extends beyond the mature 3xe2x80x2 terminus. Contained within this transcript are signals for polyadenylation and proper 3xe2x80x2 end formation. This processing at the 3xe2x80x2 end involves cleavage of the mRNA and addition of polyA to the mature 3xe2x80x2 end. By searching for consensus sequences near the polyA tract in both plant and animal mRNAs, it has been possible to identify consensus sequences that apparently are involved in polyA addition and 3xe2x80x2 end cleavage. The same consensus sequences seem to be important to both of these processes. These signals are typically a variation on the sequence AATAAA. In animal cells, some variants of this sequence that are functional have been identified; in plant cells there seems to be an extended range of functional sequences (Wickens and Stephenson, 1984; Dean et al., 1986). Because all of these consensus sequences are variations on AATAAA, they all are A+T rich sequences. This sequence is typically found 15 to 20 bp before the polyA tract in a mature mRNA. Studies in animal cells indicate that this sequence is involved in both polyA addition and 3xe2x80x2 maturation. Site directed mutations in this sequence can disrupt these functions (Conway and Wickens, 1988; Wickens et al., 1987). However, it has also been observed that sequences up to 50 to 100 bp 3xe2x80x2 to the putative polyA signal are also required; i.e., a gene that has a normal AATAAA but has been replaced or disrupted downstream does not get properly polyadenylated (Gil and Proudfoot, 1984; Sadofsky and Alwine, 1984; McDevitt et al, 1984). That is, the polyA signal itself is not sufficient for complete and proper processing. It is not yet known what specific downstream sequences are required in addition to the polyA signal, or if there is a specific sequence that has this function. Therefore, sequence analysis can only identify potential polyA signals.
In naturally occurring mRNAs that are normally polyadenylated, it has been observed that disruption of this process, either by altering the polyA signal or other sequences in the mRNA, profound effects can be obtained in the level of functional mRNA. This has been observed in several naturally occurring mRNAs, with results that are gene-specific so far.
It has been shown that in natural mRNAs proper polyadenylation is important in mRNA accumulation, and that disruption of this process can effect mRNA levels significantly. However, insufficient knowledge exists to predict the effect of changes in a normal gene. In a heterologous gene, it is even harder to predict the consequences. However, it is possible that the putative sites identified are dysfunctional. That is, these sites may not act as proper polyA sites, but instead function as aberrant sites that give rise to unstable mRNAs.
In animal cell systems, AATAAA is by far the most common signal identified in mRNAs upstream of the polyA, but at least four variants have also been found (Wickens and Stephenson, 1984). In plants, not nearly so much analysis has been done, but it is clear that multiple sequences similar to AATAAA can be used. The plant sites in Table 2 called major or minor refer only to the study of Dean et al. (1986) which analyzed only three types of plant gene. The designation of polyadenylation sites as major or minor refers only to the frequency of their occurrence as functional sites in naturally occurring genes that have been analyzed. In the case of plants this is a very limited database. It is hard to predict with any certainty that a site designated major or minor is more or less likely to function partially or completely when found in a heterologous gene such as those encoding the crystal proteins of the present invention.
The present invention provides a method for preparing synthetic plant genes which genes express their protein product at levels significantly higher than the wild-type genes which were commonly employed in plant transformation heretofore. In another aspect, the present invention also provides novel synthetic plant genes which encode non-plant proteins.
As described above, the expression of native B. thuringiensis genes in plants is often problematic. The nature of the coding sequences of B. thuringiensis genes distinguishes them from plant genes as well as many other heterologous genes expressed in plants. In particular, B. thuringiensis genes are very rich (xcx9c62%) in adenine (A) and thymine (T) while plant genes and most other bacterial genes which have been expressed in plants are on the order of 45-55% A+T.
Due to the degeneracy of the genetic code and the limited number of codon choices for any amino acid, most of the xe2x80x9cexcessxe2x80x9d A+T of the structural coding sequences of some Bacillus species are found in the third position of the codons. That is, genes of some Bacillus species have A or T as the third nucleotide in many codons. Thus A+T content in part can determine codon usage bias. In addition, it is clear that genes evolve for maximum function in the organism in which they evolve. This means that particular nucleotide sequences found in a gene from one organism, where they may play no role except to code for a particular stretch of amino acids, have the potential to be recognized as gene control elements in another organism (such as transcriptional promoters or terminators, polyA addition sites, intron splice sites, or specific mRNA degradation signals). It is perhaps surprising that such misread signals are not a more common feature of heterologous gene expression, but this can be explained in part by the relatively homogeneous A+T content (xcx9c50%) of many organisms. This A+T content plus the nature of the genetic code put clear constraints on the likelihood of occurrence of any particular oligonucleotide sequence. Thus, a gene from E. coli with a 50% A+T content is much less likely to contain any particular A+T rich segment than a gene from B. thuringiensis. 
Typically, to obtain high-level expression of the S-endotoxin genes in plants, existing structural coding sequence (xe2x80x9cstructural genexe2x80x9d) which codes for the S-endotoxin are modified by removal of ATTTA sequences and putative polyadenylation signals by site directed mutagenesis of the DNA comprising the structural gene. It is most preferred that substantially all the polyadenylation signals and ATTTA sequences are removed although enhanced expression levels are observed with only partial removal of either of the above identified sequences. Alternately if a synthetic gene is prepared which codes for the expression of the subject protein, codons are selected to avoid the ATTTA sequence and putative polyadenylation signals. For purposes of the present invention putative polyadenylation signals include, but are not necessarily limited to, AATAAA, AATAAT, AACCAA, ATATAA, AATCAA, ATACTA, ATAAAA, ATGAAA, AAGCAT, ATTAAT, ATACAT, AAAATA, ATTAAA, AATTAA, AATACA and CATAAA. In replacing the ATTTA sequences and polyadenylation signals, codons are preferably utilized which avoid the codons which are rarely found in plant genomes.
The selected DNA sequence is scanned to identify regions with greater than four consecutive adenine (A) or thymine (T) nucleotides. The A+T regions are scanned for potential plant polyadenylation signals. Although the absence of five or more consecutive A or T nucleotides eliminates most plant polyadenylation signals, if there are more than one of the minor polyadenylation signals identified within ten nucleotides of each other, then the nucleotide sequence of this region is preferably altered to remove these signals while maintaining the original encoded amino acid sequence.
The second step is to consider the about 15 to about 30 or so nucleotide residues surrounding the A+T rich region identified in step one. If the A+T content of the surrounding region is less than 80%, the region should be examined for polyadenylation signals. Alteration of the region based on polyadenylation signals is dependent upon (1) the number of polyadenylation signals present and (2) presence of a major plant polyadenylation signal.
The extended region is examined for the presence of plant polyadenylation signals. The polyadenylation signals are removed by site-directed mutagenesis of the DNA sequence. The extended region is also examined for multiple copies of the ATTTA sequence which are also removed by mutagenesis.
It is also preferred that regions comprising many consecutive A+T bases or G+C bases are disrupted since these regions are predicted to have a higher likelihood to form hairpin structure due to self-complementarity. Therefore, insertion of heterogeneous base pairs would reduce the likelihood of self-complementary secondary structure formation which are known to inhibit transcription and/or translation in some organisms. In most cases, the adverse effects may be minimized by using sequences which do not contain more than five consecutive A+T or G+C.
5.8.6 Synthetic Oligonucleotides for Mutagenesis
When oligonucleotides are used in the mutagenesis, it is desirable to maintain the proper amino acid sequence and reading frame, without introducing common restriction sites such as BglRII, HindIII, SacI, KpnI, EcoRI, NcoI, PstI and SalI into the modified gene. These restriction sites are found in poly-linker insertion sites of many cloning vectors. Of course, the introduction of new polyadenylation signals, ATTTA sequences or consecutive stretches of more than five A+T or G+C, should also be avoided. The preferred size for the oligonucleotides is about 40 to about 50 bases, but fragments ranging from about 18 to about 100 bases have been utilized. In most cases, a minimum of about 5 to about 8 base pairs of homology to the template DNA on both ends of the synthesized fragment are maintained to insure proper hybridization of the primer to the template. The oligonucleotides should avoid sequences longer than five base pairs A+T or G+C. Codons used in the replacement of wild-type codons should preferably avoid the TA or CG doublet wherever possible. Codons are selected from a plant preferred codon table (such as Table 3 below) so as to avoid codons which are rarely found in plant genomes, and efforts should be made to select codons to preferably adjust the G+C content to about 50%.
Regions with many consecutive A+T bases or G+C bases are predicted to have a higher likelihood to form hairpin structures due to self-complementarity. Disruption of these regions by the insertion of heterogeneous base pairs is preferred and should reduce the likelihood of the formation of self-complementary secondary structures such as hairpins which are known in some organisms to inhibit transcription (transcriptional terminators) and translation (attenuators).
Alternatively, a completely synthetic gene for a given amino acid sequence can be prepared, with regions of five or more consecutive A+T or G+C nucleotides being avoided. Codons are selected avoiding the TA and CG doublets in codons whenever possible. Codon usage can be normalized against a plant preferred codon usage table (such as Table 3) and the G+C content preferably adjusted to about 50%. The resulting sequence should be examined to ensure that there are minimal putative plant polyadenylation signals and ATTTA sequences.
Restriction sites found in commonly used cloning vectors are also preferably avoided. However, placement of several unique restriction sites throughout the gene is useful for analysis of gene expression or construction of gene variants.
5.8.7 xe2x80x9cPlantizedxe2x80x9d Gene Constructs
The expression of a plant gene which exists in double-stranded DNA form involves transcription of messenger RNA (mRNA) from one strand of the DNA by RNA polymerase enzyme, and the subsequent processing of the mRNA primary transcript inside the nucleus. This processing involves a 3xe2x80x2 non-translated region which adds polyadenylate nucleotides to the 3xe2x80x2 end of the RNA. Transcription of DNA into mRNA is regulated by a region of DNA usually referred to as the xe2x80x9cpromoter.xe2x80x9d The promoter region contains a sequence of bases that signals RNA polymerase to associate with the DNA and to initiate the transcription of mRNA using one of the DNA strands as a template to make a corresponding strand of RNA.
A number of promoters which are active in plant cells have been described in the literature. These include the nopaline synthase (NOS) and octopine synthase (OCS) promoters (which are carried on tumor-inducing plasmids of A. tumefaciens), the Cauliflower Mosaic Virus (CaMV) 19S and 35S promoters, the light-inducible promoter from the small subunit of ribulose bis-phosphate carboxylase (ssRUBISCO, a very abundant plant polypeptide) and the mannopine synthase (MAS) promoter (Velten et al., 1984; Velten and Schell, 1985). All of these promoters have been used to create various types of DNA constructs which have been expressed in plants (see e.g., Intl. Pat. Appl. Publ. Ser. No. WO 84/02913).
Promoters which are known or are found to cause transcription of RNA in plant cells can be used in the present invention. Such promoters may be obtained from plants or plant viruses and include, but are not limited to, the CaMV35S promoter and promoters isolated from plant genes such as ssRUBISCO genes. As described below, it is preferred that the particular promoter selected should be capable of causing sufficient expression to result in the production of an effective amount of protein.
The promoters used in the DNA constructs (i.e. chimeric plant genes) of the present invention may be modified, if desired, to affect their control characteristics. For example, the CaMV35S promoter may be ligated to the portion of the ssRUBISCO gene that represses the expression of ssRUBISCO in the absence of light, to create a promoter which is active in leaves but not in roots. The resulting chimeric promoter may be used as described herein. For purposes of this description, the phrase xe2x80x9cCaMV35Sxe2x80x9d promoter thus includes variations of CaMV35S promoter, e.g., promoters derived by means of ligation with operator regions, random or controlled mutagenesis, etc. Furthermore, the promoters may be altered to contain multiple xe2x80x9cenhancer sequencesxe2x80x9d to assist in elevating gene expression.
The RNA produced by a DNA construct of the present invention also contains a 5xe2x80x2 non-translated leader sequence. This sequence can be derived from the promoter selected to express the gene, and can be specifically modified so as to increase translation of the mRNA. The 5xe2x80x2 non-translated regions can also be obtained from viral RNA""s, from suitable eukaryotic genes, or from a synthetic gene sequence. The present invention is not limited to constructs, as presented in the following examples. Rather, the non-translated leader sequence can be part of the 5xe2x80x2 end of the non-translated region of the coding sequence for the virus coat protein, or part of the promoter sequence, or can be derived from an unrelated promoter or coding sequence. In any case, it is preferred that the sequence flanking the initiation site conform to the translational consensus sequence rules for enhanced translation initiation reported by Kozak (1984).
The cry DNA constructs of the present invention may also contain one or more modified or fully-synthetic structural coding sequences which have been changed to enhance the performance of the cry gene in plants. The structural genes of the present invention may optionally encode a fusion protein comprising an amino-terminal chloroplast transit peptide or secretory signal sequence.
The DNA construct also contains a 3xe2x80x2 non-translated region. The 3xe2x80x2 non-translated region contains a polyadenylation signal which functions in plants to cause the addition of polyadenylate nucleotides to the 3xe2x80x2 end of the viral RNA. Examples of suitable 3xe2x80x2 regions are (1) the 3xe2x80x2 transcribed, non-translated regions containing the polyadenylation signal of Agrobacterium tumor-inducing (Ti) plasmid genes, such as the nopaline synthase (NOS) gene, and (2) plant genes like the soybean storage protein (7S) genes and the small subunit of the RuBP carboxylase (E9) gene.
5.9 Method for Producing Insect-Resistant Transgenic Plants
By transforming a suitable host cell, such as a plant cell, with a recombinant cryET31, cryET40, cryET43, cryET44, cryET45, cryET46, cryET47, cryET49, cryET50, cryET52, cryET53, cryET54, cryET56, cryET57, cryET59, cryET60, cryET61, cryET62, cryET63, cryET64, cryET66, cryET67, cryET68, cryET72, cryET73, and cryET83 gene-containing segment, the expression of the encoded crystal protein (i.e., a bacterial crystal protein or polypeptide having insecticidal activity against coleopterans) can result in the formation of insect-resistant plants.
By way of example, one may utilize an expression vector containing a coding region for a B. thuringiensis crystal protein and an appropriate selectable marker to transform a suspension of embryonic plant cells, such as wheat or corn cells using a method such as particle bombardment (Maddock et al., 1991; Vasil et al., 1992) to deliver the DNA coated on microprojectiles into the recipient cells. Transgenic plants are then regenerated from transformed embryonic calli that express the insecticidal proteins.
The formation of transgenic plants may also be accomplished using other methods of cell transformation which are known in the art such as Agrobacterium-mediated DNA transfer (Fraley et al., 1983). Alternatively, DNA can be introduced into plants by direct DNA transfer into pollen (Zhou et al., 1983; Hess, 1987; Luo et al., 1988), by injection of the DNA into reproductive organs of a plant (Pena et al., 1987), or by direct injection of DNA into the cells of immature embryos followed by the rehydration of desiccated embryos (Neuhaus et al., 1987; Benbrook et al., 1986).
The regeneration, development, and cultivation of plants from single plant protoplast transformants or from various transformed explants is well known in the art (Weissbach and Weissbach, 1988). This regeneration and growth process typically includes the steps of selection of transformed cells, culturing those individualized cells through the usual stages of embryonic development through the rooted plantlet stage. Transgenic embryos and seeds are similarly regenerated. The resulting transgenic rooted shoots are thereafter planted in an appropriate plant growth medium such as soil.
The development or regeneration of plants containing the foreign, exogenous gene that encodes a polypeptide of interest introduced by Agrobacterium from leaf explants can be achieved by methods well known in the art such as described (Horsch et al., 1985). In this procedure, transformants are cultured in the presence of a selection agent and in a medium that induces the regeneration of shoots in the plant strain being transformed as described (Fraley et al., 1983).
This procedure typically produces shoots within two to four months and those shoots are then transferred to an appropriate root-inducing medium containing the selective agent and an antibiotic to prevent bacterial growth. Shoots that rooted in the presence of the selective agent to form plantlets are then transplanted to soil or other media to allow the production of roots. These procedures vary depending upon the particular plant strain employed, such variations being well known in the art.
Preferably, the regenerated plants are self-pollinated to provide homozygous transgenic plants, as discussed before. Otherwise, pollen obtained from the regenerated plants is crossed to seed-grown plants of agronomically important, preferably inbred lines. Conversely, pollen from plants of those important lines is used to pollinate regenerated plants. A transgenic plant of the present invention containing a desired polypeptide is cultivated using methods well known to one skilled in the art.
A transgenic plant of this invention thus has an increased amount of a coding region (e.g., a cryET31, cryET40, cryET43, cryET44, cryET45, cryET46, cryET47, cryET49, cryET51, cryET52, cryET53, cryET54, cryET56, cryET57, cryET59, cryET60, cryET61, cryET62, cryET63, cryET64, cryET66, cryET67, cryET68, cryET72, cryET73, and cryET83 gene) that encodes one or more CryET31, CryET40, CryET43, CryET44, CryET45, CryET46, CryET47, CryET49, CryET51, CryET52, CryET53, CryET54, CryET56, CryET57, CryET59, CryET60, CryET61, CryET62, CryET63, CryET64, CryET66, CryET67, CryET68, CryET72, CryET73, and CryET83 polypeptides. A preferred transgenic plant is an independent segregant and can transmit that gene and its activity to its progeny. A more preferred transgenic plant is homozygous for that gene, and transmits that gene to all of its offspring on sexual mating. Seed from a transgenic plant may be grown in the field or greenhouse, and resulting sexually mature transgenic plants are self-pollinated to generate true breeding plants. The progeny from these plants become true breeding lines that are evaluated for, by way of example, increased insecticidal capacity against coleopteran insects, preferably in the field, under a range of environmental conditions. The inventors contemplate that the present invention will find particular utility in the creation of transgenic plants of commercial interest including various turf grasses, wheat, corn, rice, barley, oats, a variety of ornamental plants and vegetables, as well as a number of nut- and fruit-bearing trees and plants.
5.10 Definitions
The following words and phrases have the meanings set forth below.
Expression: The combination of intracellular processes, including transcription and translation undergone by a coding DNA molecule such as a structural gene to produce a polypeptide.
Identity or percent identity: refers to the degree of similarity between two nucleic acid or protein sequences. An alignment of the two sequences is performed by a suitable computer program. A widely used and accepted computer program for performing sequence alignments is CLUSTALW v1.6 (Thompson, et al. Nucl. Acids Res., 22: 4673-4680, 1994). The number of matching bases or amino acids is divided by the total number of bases or amino acids, and multiplied by 100 to obtain a percent identity. For example, if two 580 base pair sequences had 145 matched bases, they would be 25 percent identical. If the two compared sequences are of different lengths, the number of matches is divided by the shorter of the two lengths. For example, if there were 100 matched amino acids between 200 and a 400 amino acid proteins, they are 50 percent identical with respect to the shorter sequence. If the shorter sequence is less than 150 bases or 50 amino acids in length, the number of matches are divided by 150 (for nucleic acid bases) or 50 (for amino acids), and multiplied by 100 to obtain a percent identity.
Promoter: A recognition site on a DNA sequence or group of DNA sequences that provide an expression control element for a structural gene and to which RNA polymerase specifically binds and initiates RNA synthesis (transcription) of that gene.
Regeneration: The process of growing a plant from a plant cell (e.g., plant protoplast or explant).
Structural gene: A polynucleotide sequence that encodes a polypeptide, that is expressed to produce a polypeptide, or which is cryptic or incapable of expression in its natural host cell but which can be isolated and purified and operably linked to at least a promoter functional in one or more host cell types to express the encoded polypeptide.
Transformation: A process of introducing an exogenous DNA sequence (e.g., a vector, a recombinant DNA molecule) into a cell or protoplast in which that exogenous DNA is incorporated into a chromosome or is capable of autonomous replication.
Transformed cell: A cell whose DNA has been altered by the introduction of an exogenous DNA molecule into that cell.
Transgenic cell: Any cell derived or regenerated from a transformed cell or derived from a transgenic cell. Exemplary transgenic cells include plant calli derived from a transformed plant cell and particular cells such as leaf, root, stem, e.g., somatic cells, or reproductive (germ) cells obtained from a transgenic plant.
Transgenic plant: A plant or progeny thereof derived from a transformed plant cell or protoplast, wherein the plant DNA contains an introduced exogenous DNA molecule not originally present in a native, non-transgenic plant of the same strain. The terms xe2x80x9ctransgenic plantxe2x80x9d and xe2x80x9ctransformed plantxe2x80x9d have sometimes been used in the art as synonymous terms to define a plant whose DNA contains an exogenous DNA molecule. However, it is thought more scientifically correct to refer to a regenerated plant or callus obtained from a transformed plant cell or protoplast as being a transgenic plant, and that usage will be followed herein.
Vector: A DNA molecule capable of replication in a host cell and/or to which another DNA segment can be operatively linked so as to bring about replication of the attached segment. A plasmid is an exemplary vector.
5.11 Isolating Homologous Gene and Gene Fragments
The genes and xcex4-endotoxins according to the subject invention include not only the full length sequences disclosed herein but also fragments of these sequences, or fusion proteins, which retain the characteristic insecticidal activity of the sequences specifically exemplified herein.
It should be apparent to a person skill in this art that insecticidal xcex4-endotoxins can be identified and obtained through several means. The specific genes, or portions thereof, may be obtained from a culture depository, or constructed synthetically, for example, by use of a gene machine. Variations of these genes may be readily constructed using standard techniques for making point mutations. Also, fragments of these genes can be made using commercially available exonucleases or endonucleases according to standard procedures. For example, enzymes such as Bal31 or site-directed mutagenesis can be used to systematically cut off nucleotides from the ends of these genes. Also, genes which code for active fragments may be obtained using a variety of other restriction enzymes. Proteases may be used to directly obtain active fragments of these xcex4-endotoxins.
Equivalent xcex4-endotoxins and/or genes encoding these equivalent xcex4-endotoxins can also be isolated from Bacillus strains and/or DNA libraries using the teachings provided herein. For example, antibodies to the xcex4-endotoxins disclosed and claimed herein can be used to identify and isolate other xcex4-endotoxins from a mixture of proteins. Specifically, antibodies may be raised to the portions of the xcex4-endotoxins which are most constant and most distinct from other B. thuringiensis xcex4-endotoxins. These antibodies can then be used to specifically identify equivalent xcex4-endotoxins with the characteristic insecticidal activity by immunoprecipitation, enzyme linked immunoassay (ELISA), or Western blotting.
A further method for identifying the xcex4-endotoxins and genes of the subject invention is through the use of oligonucleotide probes. These probes are nucleotide sequences having a detectable label. As is well known in the art, if the probe molecule and nucleic acid sample hybridize by forming a strong bond between the two molecules, it can be reasonably assumed that the probe and sample are essentially identical. The probe""s detectable label provides a means for determining in a known manner whether hybridization has occurred. Such a probe analysis provides a rapid method for identifying formicidal xcex4-endotoxin genes of the subject invention.
The nucleotide segments which are used as probes according to the invention can be synthesized by use of DNA synthesizers using standard procedures. In the use of the nucleotide segments as probes, the particular probe is labeled with any suitable label known to those skilled in the art, including radioactive and non-radioactive labels. Typical radioactive labels include 32P, 125I, 35S, or the like. A probe labeled with a radioactive isotope can be constructed from a nucleotide sequence complementary to the DNA sample by a conventional nick translation reaction, using a DNase and DNA polymerase. The probe and sample can then be combined in a hybridization buffer solution and held at an appropriate temperature until annealing occurs. Thereafter, the membrane is washed free of extraneous materials, leaving the sample and bound probe molecules typically detected and quantified by autoradiography and/or liquid scintillation counting.
Non-radioactive labels include, for example, ligands such as biotin or thyroxine, as well as enzymes such as hydrolases or peroxidases, or the various chemiluminescers such as luciferin, or fluorescent compounds like fluorescein and its derivatives. The probe may also be labeled at both ends with different types of labels for aease of separation, as, for example, by using an isotopic label at the end mentioned above and a biotin label at the other end.
Duplex formation and stability depend on substantial complementarity between the two strands of a hybrid, and, as noted above, a certain degree of mismatch can be tolerated. Therefore, the probes of the subject invention include mutations (both single and multiple), deletions, insertions of the described sequences, and combinations thereof, wherein said mutations, insertions and deletions permit formation of stable hybrids with the target polynucleotide of interest. Mutations, insertions, and deletions can be produced in a given polynucleotide sequence in many ways, by methods currently known to an ordinarily skilled artisan, and perhaps by other methods which may become known in the future.
The potential variations in the probes listed is due, in part, to the redundancy of the genetic code. Because of the redundancy of the genetic code, i.e., more than one coding nucleotide triplet (codon) can be used for most of the amino acids used to make proteins. Therefore different nucleotide sequences can code for a particular amino acid. Thus, the amino acid sequences of the B. thuringiensis xcex4-endotoxins and peptides can be prepared by equivalent nucleotide sequences encoding the same amino acid sequence of the protein or peptide. Accordingly, the subject invention includes such equivalent nucleotide sequences. Also, inverse or complement sequences are an aspect of the subject invention and can be readily used by a person skilled in this art. In addition it has been shown that proteins of identified structure and function may be constructed by changing the amino acid sequence if such changes do not alter the protein secondary structure (Kaiser and Kezdy, 1984). Thus, the subject invention includes mutants of the amino acid sequence depicted herein which do not alter the protein secondary structure, or if the structure is altered, the biological activity is substantially retained. Further, the invention also includes mutants of organisms hosting all or part of a xcex4-endotoxin encoding a gene of the invention. Such mutants can be made by techniques well known to persons skilled in the art. For example, UV irradiation can be used to prepare mutants of host organisms. Likewise, such mutants may include asporogenous host cells which also can be prepared by procedures well known in the art.